Low-cost carbon-doped low-nickel-iron-based medium-entropy alloy and application thereof

Abstract

The invention discloses a low-cost carbon-doped low-nickel iron-based medium-entropy alloy and application thereof, and aims to solve the technical problem that a low-nickel FeNiCrSiAl iron-based medium-entropy alloy is difficult to deform and process. According to the low-nickel FeNiCrSiAl iron-based medium-entropy alloy, a trace of C element is added into the low-nickel FeNiCrSiAl iron-based medium-entropy alloy, so that the alloy is converted into an FCC and BCC dual-phase structure from a single BCC phase, and the rollability of the alloy is remarkably enhanced. According to the low-nickel FeNiCrSiAl iron-based medium-entropy alloy and the preparation method thereof, the alloy cost is greatly reduced while the using performance of the low-nickel FeNiCrSiAl iron-based medium-entropy alloy is guaranteed, and development and application of the low-nickel FeNiCrSiAl iron-based medium-entropy alloy are promoted.

Description

Technical Field

[0001] The present invention relates to the field of alloy technology, and specifically to a low-cost carbon-doped low-nickel iron-based medium-entropy alloy and its application. Background Art

[0002] Middle-entropy alloys (MEAs) are multi-element alloys composed of 3 to 5 main elements, with the atomic percentage of each element ranging from 5% to 35%, and their entropy value is between that of traditional metals and high-entropy alloys. As one of the representatives of MEAs, FeNiCrSiAl medium-entropy alloys exhibits excellent properties, including high strength, high toughness, excellent corrosion resistance and oxidation resistance. These properties make FeNiCrSiAl medium-entropy alloys have great application potential in high-end fields such as aerospace, automobile manufacturing, and energy.

[0003] However, when designing the composition of iron-based medium-entropy alloys, in order to ensure their excellent mechanical properties, more precious metal elements such as Co, Ni, and Mo are still added, resulting in high costs, which in turn restricts the industrial application of medium / high-entropy alloys. For example, in the FeNiCrSiAl medium-entropy alloy system, Ni is a precious metal element. In order to reduce the cost of the alloy system, researchers are committed to reducing the Ni content. However, Ni is an element that promotes the formation of face-centered cubic (FCC) structure. When its content is low to a critical value, the face-centered cubic FCC will gradually transform into a body-centered cubic (BCC) structure. The BCC structure has the characteristics of hard and brittle mechanical properties, which easily leads to the difficulty of deformation processing of alloys dominated by BCC.

[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 of this application have found through long-term research that Fe 64 Ni 11 Cr 15 Si7Al3 is a single BCC phase in the cast state, which has the characteristics of hard and brittle mechanical properties. However, after adding a trace amount of C element to the alloy system, the alloy will form a dual-phase structure, which can solve the technical problem that low-nickel FeNiCrSiAl iron-based medium-entropy alloys are difficult to deform. Therefore, the present disclosure provides a low-cost carbon-doped low-nickel iron-based medium-entropy alloy and its application.

[0006] In one aspect of the present disclosure, a low-cost carbon-doped low-nickel iron-based medium-entropy alloy is provided, wherein the alloy expression is (Fe 64 Ni 11 Cr15 Si7Al3) 100-x C x , 0 <x<0.5。

[0007] In some embodiments of the present disclosure, the low-cost carbon-doped low-nickel iron-based medium entropy alloy is characterized in that its alloy expression is (Fe 64 Ni 11 Cr 15 Si7Al3) 100-x C x , 0.15≤x≤0.25.

[0008] In some embodiments of the present disclosure, the low-cost carbon-doped low-nickel iron-based medium-entropy alloy is made of the following raw materials: Fe 63.84%, Ni 10.9725%, Cr 14.9625%, Si 6.9825%, Al2.9925%, and C 0.25%.

[0009] In some embodiments of the present disclosure, the low-cost carbon-doped low-nickel iron-based medium-entropy alloy is made of the following raw materials: Fe 63.904%, Ni 10.9835%, Cr 14.9775%, Si 6.9895%, Al2.9955%, and C 0.15%.

[0010] According to a second aspect of the present disclosure, a method for preparing a low-cost carbon-doped low-nickel iron-based medium-entropy alloy is provided, comprising the following steps: (1) preparing alloy smelting raw materials according to the above atomic percentages, mixing them and then performing vacuum melting to obtain alloy liquid; (2) casting the alloy liquid to obtain a cast alloy; (2) performing 80-85% multi-pass rolling on the cast alloy to obtain an alloy plate; (3) After rolling, the alloy plate is annealed at 750-850° C. for 8-12 min, and finally liquid-cooled.

[0011] According to a third aspect of the present disclosure, the above-mentioned low-cost carbon-doped low-nickel iron-based medium-entropy alloy is applied in a low-temperature environment and / or in the preparation of low-temperature resistant products.

[0012] One or more technical solutions provided in the embodiments of the present application have at least any of the following technical effects or advantages: Reasonable addition of trace C elements in the iron-based medium entropy alloy FeNiCrSiAl can not only ensure the cost of the alloy, but also achieve the rollability of the low-nickel FeNiCrSiAl iron-based medium entropy alloy. C plays the role of an interstitial solid solution element in the alloy FeNiCrSiAl, which not only plays a role in solid solution strengthening, but also effectively promotes the formation of FCC structure in the alloy. Adding 0.15 at.% C elements to the iron-based medium entropy alloy FeNiCrSiAl can gradually transform the single BCC phase in the cast state into a FCC+BCC dual-phase structure; in-depth research has found that when the C element increases to 0.5 at.%, carbides appear, and after rolling annealing, it begins to yield at low temperature and then breaks at the yield platform. When the C content increases to 2 at.%, it cannot be rolled.

[0013] The present invention greatly reduces the alloy cost while maintaining the performance of the low-nickel FeNiCrSiAl iron-based medium-entropy alloy, which is beneficial to promoting the development and application of the low-nickel FeNiCrSiAl iron-based medium-entropy alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 1 is the cast X-ray diffraction pattern (XRD) of Ni11, Ni11C0.15 and Ni11C0.25 in one embodiment of the present application.

[0015] Figure 2 This is the cast backscattered electron image (BSE) of Ni11, Ni11C0.15 and Ni11C0.25 in one embodiment of the present application.

[0016] Figure 3 The following are the backscattered electron image (BSE) and transmission electron microscope image (TEM) of the cast Ni11C0.25 in one embodiment of the present application.

[0017] Figure 4 This is the X-ray diffraction pattern (XRD) of Ni11C0.15 and Ni11C0.25 in the rolled annealed state in one embodiment of the present application.

[0018] Figure 5 This is a transmission electron microscope (TEM) image of Ni11C0.25 in a rolled annealed state in an embodiment of the present application.

[0019] Figure 6 Graph showing the room temperature (298K) and low temperature (77K) tensile curves of Ni11C0.15, Ni11C0.25 and Ni11C0.35 alloys in rolled annealed state in one embodiment of the present application.

[0020] Figure 7 The figure shows the backscattered electron image (BSE) and energy dispersive X-ray spectrometer (EDS) of the Ni11C2 alloy as-cast in one embodiment of the present application.

[0021] Figure 8 In an embodiment of the present application, the tensile curve diagrams at room temperature (298K) and low temperature (77K) of Ni11C0.25, Ni11C0.5, Ni11C1, and Ni11C1.5 alloys in the rolled and annealed state.

[0022] Fig. 9 In an embodiment of the present application, the transmission electron microscope image (TEM) of Ni11C0.5 alloy in the rolled and annealed state.

[0023] In the above figures, AC represents the as-cast state; ANN represents the rolled and annealed state. Detailed implementation manners

[0024] 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 of the specification and specific implementation manners.

[0025] In the following embodiments, the instrument equipment involved, unless otherwise specified, are all conventional instrument equipment; the raw materials involved, unless otherwise specified, are all commercially available conventional raw materials; the processing and manufacturing methods and detection methods involved, unless otherwise specified, are all conventional methods.

[0026] Embodiment 1 This example discloses a preparation method of a low-cost carbon-doped low-nickel iron-based medium-entropy alloy, and the chemical formula of the alloy is (Fe 64 Ni 11 Cr 15 Si7Al3) 100-x C x , 0 < x < 0.5. Using elements with a purity greater than 99.9 wt% as raw materials, weighing each raw material according to the above atomic percentages, placing all the raw materials in a high-vacuum arc furnace under argon protection, setting the melting current to 180 - 200 A, melting at least four times under electromagnetic stirring to ensure uniform composition, turning it over before each melting, and the electromagnetic stirring time each time is not less than 30 s. Subsequently, it is cast into a water-cooled copper mold of 10*10*30 mm 3 to obtain an as-cast alloy ingot. Finally, the obtained as-cast alloy ingot is subjected to multi-pass room-temperature rolling with a reduction of 0.2 mm each time, the rolling speeds of the upper and lower rolls are both ~10 revolutions / min, and the rolled plate is annealed at 800 °C for 10 min. After the annealing treatment is completed, water cooling is carried out to obtain a trace carbon-doped low-nickel iron-based medium-entropy alloy.

[0027] Embodiment 2 According to the composition of (Fe 64 Ni 11 Cr 15 Si7Al3) 99.85 C0.15 The ingredients were prepared according to the composition of the embodiment 1, and the alloy Ni11C0.15 was obtained.

[0028] Embodiment 3 According to the composition (Fe 64 Ni 11 Cr 15 Si7Al3) 99.75 C 0.25 The composition is prepared and the alloy Ni11C0.25 is obtained according to the alloy preparation method described in Example 1.

[0029] Embodiment 4 According to the composition (Fe 64 Ni 11 Cr 15 Si7Al3) 99.65 C 0.35 The composition is prepared and the alloy Ni11C0.35 is obtained according to the alloy preparation method described in Example 1.

[0030] The X-ray diffraction analysis and backscattered electron imaging analysis of Ni11C0.15 and Ni11C0.25 alloys were performed in the cast state and compared with Ni11. The results are as follows: Figure 1 and Figure 2 As shown, the results showed that Fe 64 Ni 11 Cr 15 The as-cast structure of Si7Al3 alloy (Ni11-AC) is a single BCC structure. After adding 0.15%C and 0.25%C (C0.15-AC and C0.25-AC), the structure changes to FCC+BCC dual-phase structure, in which the FCC content in C0.25-AC is higher than that in C0.15-AC. Therefore, backscattered electron imaging analysis and transmission electron microscopy analysis were performed on C0.25-AC, and the results ( Figure 3 ) showed that there was a B2-structured nano-precipitate phase enriched with Ni and Al elements in the BCC phase of the C0.25-AC alloy, and the average grain diameter of the precipitate phase was about 19 nm, indicating that phase transformation and precipitation strengthening processes occurred in the C0.25-AC alloy, which could significantly improve its mechanical properties.

[0031] Furthermore, the Ni11C0.15 and Ni11C0.25 alloys were rolled and annealed, and their phases and crystal structures were observed. The results showed that (e.g. Figure 4As shown in the figure, the Ni11-AC alloy without C addition cannot be rolled because it has a single BCC structure. After 85% rolling and annealing at 800℃-10min, the two cast alloys Ni11C0.15 (C0.15-ANN) and Ni11C0.25 (C0.25-ANN) still have FCC+BCC dual-phase structures, and the C0.25-ANN alloy has a complex microstructure, including ultrafine grains, nano-second phases, annealing twins and dislocations, among which the nano-second phase is B2 (NiAl) phase with an average grain diameter of about 74nm ( Figure 5 ).

[0032] The mechanical properties of three alloys, Ni11C0.15, Ni11C0.25 and Ni11C0.35, at room temperature (298K) and low temperature (77K) were studied. Figure 6 As shown in Table 1, the results show that Ni11C0.15 and Ni11C0.25 not only have a good match of strength and plasticity at room temperature, but also have excellent strength and plasticity at low temperature 77K. The strength and plasticity of Ni11C0.35 at low temperature are slightly inferior to those of Ni11C0.15 and Ni11C0.25, but can still meet the basic mechanical properties requirements.

[0033] Table 1 Comparison of mechanical properties of alloys in the examples .

[0034] Comparative Example 1 According to the composition (Fe 64 Ni 11 Cr 15 Si7Al3) 99.5 C 0.5 The composition is prepared and the alloy Ni11C0.5 is obtained according to the alloy preparation method described in Example 1.

[0035] Comparative Example 2 According to the composition (Fe 64 Ni 11 Cr 15 Si7Al3) 99 The composition of C1 was prepared, and the alloy Ni11C1 was prepared according to the alloy preparation method described in Example 1.

[0036] Comparative Example 3 According to the composition (Fe 64 Ni 11 Cr 15 Si7Al3) 98.5 C 1.5 The composition is prepared and the alloy Ni11C1.5 is obtained according to the alloy preparation method described in Example 1.

[0037] Comparative Example 4 According to the composition (Fe 64 Ni 11 Cr 15 Si7Al3) 98 The composition of C2 was prepared, and the alloy Ni11C2 was obtained according to the alloy preparation method described in Example 1.

[0038] The mechanical properties and microstructure of the alloys prepared in the above comparative examples 1 to 4 were tested and compared with the alloy prepared in Example 3. The results are shown in Table 2. Figure 7 As shown, the results show that in Fe 64 Ni 11 Cr 15 When the C content in Si7Al3 alloy reaches 2%, a large amount of Cr-rich carbides are formed in the alloy ( Figure 7 ), since these carbides themselves have high hardness and brittleness, their large-scale formation can easily lead to stress concentration, thereby causing alloy cracks, which in turn affects the alloy's ability to continuously plastically deform, making it impossible to roll smoothly.

[0039] Furthermore, when Fe 64 Ni 11 Cr 15 When the C content in Si7Al3 alloy reaches 0.5~1.5%, although the rolled annealed alloy can be rolled smoothly at room temperature, its mechanical properties and plasticity are significantly reduced in low temperature environment ( Figure 8 ). In particular, when Fe 64 Ni 11 Cr 15 When the C content in Si7Al3 alloy is 0.5%, some carbides are formed in the rolled annealed alloy ( Fig. 9 ), the large amount of solid solution of carbon and the formation of carbides are the main reasons for the yield platform fracture of the alloy under low temperature conditions (the solid solution of carbon increases the hardness of the material, and the formation of carbides may lead to stress concentration. These factors work together to make the alloy more likely to fracture at the yield platform at low temperatures).

[0040] Table 2 Comparison of mechanical properties of alloys in comparative examples .

[0041] Although some preferred embodiments of the present application 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 invention.

[0042] 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 carbon-doped low-nickel iron-based medium-entropy alloy, the alloy expression of which is (Fe 64 Ni 11 Cr 15 Si7Al3) 100-x C x , 0 <x<0.5。 2. The low-cost carbon-doped low-nickel iron-based medium-entropy alloy according to claim 1, characterized in that: Its alloy expression is (Fe 64 Ni 11 Cr 15 Si7Al3) 100-x C x , 0.15≤x≤0.

25.

3. The low-cost carbon-doped low-nickel iron-based medium-entropy alloy according to claim 1, characterized in that: Made of the following raw materials: Fe 63.84%, Ni 10.9725%, Cr 14.9625%, Si 6.9825%, Al 2.9925%, C 0.25%.

4. The low-cost carbon-doped low-nickel iron-based medium-entropy alloy according to claim 1, characterized in that: Made of the following raw materials: Fe 63.904%, Ni 10.9835%, Cr 14.9775%, Si 6.9895%, Al 2.9955%, C 0.15%.

5. Use of the low-cost carbon-doped low-nickel iron-based medium-entropy alloy according to any one of claims 1 to 4 in a low-temperature environment and / or in the preparation of low-temperature resistant products.

6. A method for preparing a low-cost carbon-doped low-nickel iron-based medium-entropy alloy, comprising the following steps: (1) preparing alloy smelting raw materials according to the atomic percentage of claim 1, mixing them and then performing vacuum melting to obtain alloy liquid; (2) casting the alloy liquid to obtain a cast alloy; (2) performing 80-85% multi-pass rolling on the cast alloy to obtain an alloy plate; (3) The alloy plate is annealed at 750-850° C. for 8-12 min, and then liquid-cooled.

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