Netted heterostructure casting high-entropy alloy with good mechanical property and preparation and application of reticular heterostructure casting high-entropy alloy

Abstract

The invention relates to a net-shaped heterostructure cast high-entropy alloy with good mechanical properties and preparation and application thereof, and aims to solve the technical problems of high production cost and long period caused by the dependence of introduction of high-cost elements or a complex process in the conventional high-entropy alloy. The CrFexNiAl0. 28Ti0. 12 as-cast high-entropy alloy is prepared by taking CrFeNiAl0. 28 as a matrix component, optimizing the alloy design by introducing a Ti element and adjusting the content of an Fe element and combining a vacuum arc melting and suction casting process. According to the method, Ti is reasonably added into the CrFeNiAl0.28 series alloy, the content of Fe is regulated and controlled to optimize the mechanical property of the CrFeNiAl0.28 series alloy, meanwhile, adverse effects caused by the Fe are overcome or balanced, and the net-shaped bionic heterostructure as-cast high-entropy alloy which is high in strength, good in plasticity and low in cost is developed.

Description

Technical Field

[0001] The present invention relates to the technical field of alloys, and particularly relates to a cast high-entropy alloy with a reticular heterogeneous structure having good mechanical properties, and its preparation and application. Background Art

[0002] High-Entropy Alloys (HEAs) are a new type of multi-principal element alloy material. Due to their unique high-entropy effect, lattice distortion effect, slow diffusion effect, and cocktail effect, they exhibit significant advantages in mechanical properties and corrosion resistance, and have gradually become a research hotspot in the field of materials science and engineering. Traditional high-entropy alloys are usually composed of five or more principal elements in equiatomic or near-equiatomic ratios, and form a multi-phase structure during the cooling process through solid-state phase transformation, thereby obtaining excellent as-cast properties. Taking the CrFeNiAl 0.28 series of as-cast high-entropy alloys as an example, they show high tensile strength (such as >500 MPa) and good ductility (fracture strain >30%) at room temperature, and do not rely on precious elements (such as Co, etc.) or complex subsequent processes (such as rolling, hot forging, heat treatment), which reduces the production cost and process cycle to a certain extent.

[0003] However, with the continuous improvement of the performance requirements of alloy materials in different engineering fields, how to further optimize the strength of alloy materials while maintaining sufficient plasticity has become a difficult problem to be solved urgently in the composition design of high-entropy alloys. In the prior art, the alloy performance is improved by adding precious elements (such as Co, etc.) or introducing complex processes, but this also leads to an increase in preparation cost and a decrease in production efficiency, seriously restricting its application.

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

[0005] It is found through research that the distribution and content of FCC (face-centered cubic) and BCC (body-centered cubic) phases in the CrFeNiAl series of high-entropy alloys have a significant impact on their mechanical properties. The FCC structure usually exhibits high plasticity and toughness, but low strength. The BCC phase has high strength due to lattice distortion and short-range order (SRO) effects, but poor plasticity; therefore, an excellent balance between the two is required. Based on the in-depth understanding of the mechanism of the CrFeNiAl series of high-entropy alloys and combined with long-term research experience, the present inventors comprehensively regulate the alloy phase composition and microstructure by selecting and doping Ti elements and adjusting the content of Fe elements, thereby optimizing their mechanical properties, while overcoming or balancing the adverse effects brought by them, and developing a cast high-entropy alloy with a reticular heterogeneous phase structure having high strength, good plasticity and low cost.

[0006] In one aspect of the present disclosure, a reticulated heterogeneous structure cast high-entropy alloy is provided, and its alloy expression is CrFe x NiAl 0.28 Ti 0.12 , and the molar ratio of each element is Cr:Fe:Ni:Al:Ti = 1:x:1:0.28:0.12, and 0.9 ≤ x ≤ 1.45.

[0007] In some embodiments of the present disclosure, 1.0 ≤ x ≤ 1.40.

[0008] In some embodiments of the present disclosure, 1.1 ≤ x ≤ 1.30.

[0009] In some embodiments of the present disclosure, the high-entropy alloy contains an FCC phase and a BCC phase, and part (more than 90%) or all of the BCC phase is wrapped in a reticulated structure composed of island-shaped or / and side-plate-shaped FCC phases. Among them, the FCC phase has relatively low strength and good plasticity and belongs to the soft phase; the BCC phase has relatively high strength and poor plasticity and belongs to the hard phase; the structure in which the FCC soft phase wraps the BCC hard phase is beneficial to improving the overall mechanical properties of the alloy, enabling good matching of strength and plasticity (taking into account both the strength and plasticity of the alloy material).

[0010] In some embodiments of the present disclosure, the BCC phase has a cellular structure, in which L21 nanoparticles are dispersed, which can further improve the strength of the BCC phase.

[0011] According to the second aspect of the present disclosure, a preparation method of a reticulated heterogeneous structure cast high-entropy alloy is provided, including the following steps: (1) Configure each alloy smelting raw material according to the above element molar ratio, and mix and melt it under vacuum or inert atmosphere to obtain an alloy liquid; (2) Repeatedly melt at least 4 times, and cast the obtained alloy liquid into a mold to obtain the corresponding as-cast alloy ingot / item.

[0012] According to the third aspect of the present disclosure, the above low-cost reticulated heterogeneous structure cast high-entropy alloy is applied to the manufacturing of chemical engineering, energy, machinery, shipbuilding, marine or aerospace engineering equipment.

[0013] One or more technical solutions provided in the embodiments of the present disclosure have at least any one of the following technical effects or advantages: 1. By reasonably adjusting the element ratios of the CrFeNiAl system and doping with Ti element, a cast high-entropy alloy with good mechanical properties (both high yield strength and good plasticity) was developed; the yield strength of this alloy at room temperature (298K) is 906 - 978 MPa, the ultimate tensile strength is 1313 - 1337 MPa, and the fracture strain is between 21.0% and 23.4%.

[0014] 2. Based on the CrFeNiAl system, doping with Ti element and reasonably regulating the content of Fe element, compared with the alloy of the CrFeNiAl system with low Fe element content, the obtained alloy material not only has high strength characteristics, but also can maintain good plasticity at high strength. Description of the Drawings

[0015] Figure 1 It is the cast X-ray diffraction pattern (XRD) of the alloy materials obtained in Examples 2 to 4 of the present disclosure.

[0016] Figure 2 It is the SEM morphology of the alloy materials obtained in Examples 1 to 4 of the present disclosure.

[0017] Figure 3 It is the tensile stress-strain curve of the alloy materials obtained in Examples 1 to 4 of the present disclosure.

[0018] Figure 4 It is the stress-strain curve of the cast high-entropy alloy in the embodiments of the present disclosure.

[0019] Figure 5 It is the TEM and elemental analysis diagram of Fe1.1 in the embodiments of the present disclosure.

[0020] Figure 6 It is the trend diagram of Fe content - yield strength (YS) and tensile strength (UTS) in the embodiments of the present disclosure.

[0021] Figure 7 It is the trend diagram of Fe content - uniform elongation rate (ε) in the embodiments of the present disclosure. Detailed Embodiments

[0022] 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 embodiments.

[0023] 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 preparation methods and detection methods involved, unless otherwise specified, are all conventional methods.

[0024] Example 1. Preparation of High-Entropy Alloy CrFeNiAl 0.28 Ti0.12 According to CrFeNiAl 0.28 Ti 0.12 The proportion of elements in the alloy, with a purity greater than 99.9wt% of elements (chromium, iron, nickel, aluminum and titanium) as raw materials, was prepared by arc melting in Ar atmosphere with a nominal composition of CrFeNiAl 0.28 Ti 0.12 The resulting ingot was remelted 5 times under electromagnetic stirring to ensure uniformity and suction cast into 10×10×50 mm 3 Rectangular rod-shaped alloy specimen (named Fe1.0).

[0025] A dog-bone-shaped flat specimen of 10 mm × 2 mm × 1.5 mm was cut from the above rectangular rod-shaped specimen. The specimen was stretched at a deformation rate of 0.1 mm / min using a screw-driven Suns UTM 5105 testing machine at room temperature. The XRD results are shown in Figure 1 , SEM morphology Figure 2 Its yield strength, tensile strength and uniform elongation are shown in Table 1.

[0026] Example 2: Preparation of high entropy alloy CrFe 1.1 NiAl 0.28 Ti 0.12 According to CrFe 1.1 NiAl 0.28 Ti 0.12 The proportion of elements in the alloy, with a purity greater than 99.9wt% of elements (chromium, iron, nickel, aluminum and titanium) as raw materials, was prepared by arc melting in Ar atmosphere with a nominal composition of CrFe 1.1 NiAl 0.28 Ti 0.12 All the ingots were remelted 5 times under electromagnetic stirring to ensure uniformity and suction cast into 10×10×50 mm 3 Rectangular rod-shaped alloy specimen (named Fe1.1).

[0027] A dog-bone-shaped flat specimen of 10 mm × 2 mm × 1.5 mm was cut from a rectangular rod-shaped specimen. The specimen was stretched at a deformation rate of 0.1 mm / min using a screw-driven Suns UTM 5105 testing machine at room temperature. The XRD results are shown in Figure 1 , SEM morphology Figure 2 , TEM and elemental analysis see Figure 5 Its yield strength, tensile strength and uniform elongation are shown in Table 1.

[0028] Example 3: Preparation of high entropy alloy CrFe 1.2 NiAl 0.28 Ti 0.12 According to CrFe 1.2 NiAl 0.28 Ti 0.12 The proportion of elements in the alloy, with a purity greater than 99.9wt% of elements (chromium, iron, nickel, aluminum and titanium) as raw materials, was prepared by arc melting in Ar atmosphere with a nominal composition of CrFe 1.2 NiAl 0.28 Ti 0.12 All ingots were remelted at least 5 times under electromagnetic stirring to ensure uniformity and suction cast into 10×10×50 mm 3 Rectangular rod-shaped alloy specimen (named Fe1.2).

[0029] A dog-bone-shaped flat specimen of 10 mm × 2 mm × 1.5 mm was cut from a rectangular rod-shaped specimen. The specimen was stretched at a deformation rate of 0.1 mm / min using a screw-driven Suns UTM 5105 testing machine at room temperature. The XRD results are shown in Figure 1 , SEM morphology Figure 2 Its yield strength, tensile strength and uniform elongation are shown in Table 1.

[0030] Example 4: Preparation of high entropy CrFe 1.3 NiAl 0.28 Ti 0.12 According to CrFe 1.3 NiAl 0.28 Ti 0.12 The proportion of elements in the alloy, with a purity greater than 99.9wt% of elements (chromium, iron, nickel, aluminum and titanium) as raw materials, was prepared by arc melting in Ar atmosphere with a nominal composition of CrFe 1.3 NiAl 0.28 Ti 0.12 All the ingots were remelted 5 times under electromagnetic stirring to ensure uniformity and suction cast into 10×10×50 mm 3 The rectangular rod alloy sample (named Fe1.3) was tested and its XRD results are shown in Figure 1 , SEM morphology Figure 2 Its yield strength, tensile strength and uniform elongation are shown in Table 1.

[0031] Flat specimens in the shape of dog bones with dimensions of 10 mm × 2 mm × 1.5 mm were cut from a cuboid bar-shaped specimen. Tensile tests were carried out on a screw-driven Suns UTM 5105 testing machine at room temperature with a deformation rate of 0.1 mm / min. After testing, the XRD results are shown in Figure 1 , the SEM morphology is shown in Figure 2 , the TEM and elemental analysis are shown in Figure 6 , and the yield strength, tensile strength, and uniform elongation indexes are shown in Table 1.

[0032] Table 1 Yield strength (YS), tensile strength (UTS), and uniform elongation (ε) indexes of each alloy .

[0033] From Figure 1 , it can be seen that each alloy has a dual-phase structure of FCC plus BCC.

[0034] From the SEM images of Examples 1 to 4 ( Figure 2 ), it can be seen that the microstructure of the alloy consists of a gray network structure wrapping a black cellular structure, and nanoparticles are dispersed in the black cellular structure. Other analyses have proven that the gray area is the FCC phase, the black area is the BCC phase, and L21 nanophases are dispersed in the black BCC phase area. The FCC phase is in the form of side plates or / and islands. With the increase in Fe content, the network structure composed of island-shaped or / and side plate-shaped FCC phases gradually coarsens and its continuity increases.

[0035] From the stress-strain curves of Examples 1 to 4 ( Figure 3 ) and Table 1, it can be seen that the yield strength of the alloy material can reach 978 MPa, the ultimate tensile strength can reach 1337 MPa, and it has high mechanical properties. The elongation of the alloy material can reach 23.4%.

[0036] From Figure 4 , it can be seen the changing trends of the yield strength (YS), ultimate tensile strength (UTS), and uniform elongation (ε) of this series of as-cast high-entropy alloys. This series of as-cast high-entropy alloys has excellent strength characteristics, and the combination of the FCC network structure and the BCC cellular structure formed by changing the Fe element content has a good synergistic effect, which is conducive to stress distribution and reduces stress concentration, and can maintain good plasticity at high strength.

[0037] Figure 5These are TEM and elemental analysis diagrams, from which it can be seen that the change in Fe element affects the phase transformation behavior of the as-cast high-entropy alloy. During solidification, this as-cast high-entropy alloy undergoes solid-state phase transformation while maintaining the stability of its microstructure. Its structure consists of an FCC network phase (including island / plate-like morphologies), a BCC cellular phase with dispersed L21 nanoparticles, and L21 bulk precipitates (including BCC laths) embedded in the FCC matrix. As the Fe content increases, the FCC network structure coarsens and its continuity significantly improves.

[0038] Figure 6 This is a graph of Fe content - yield strength and tensile strength trends. Figure 7 This is a graph of Fe content - uniform elongation trends. Generally speaking, for a new generation of high-strength steels, the yield strength needs to be greater than 800 MPa, the ultimate tensile strength needs to be greater than 1200 MPa, and the elongation needs to be greater than 8%. According to this standard and referring to Figure 6 it can be known that when the molar fraction of Fe is less than 1.45, the yield strength and ultimate tensile strength meet the requirements; from Figure 7 it can be known that when the molar fraction of Fe is above 0.9, it meets the requirements of the new generation of high-strength steels for elongation; therefore, considering meeting the above index requirements, the molar fraction range of Fe is 0.9 - 1.45.

[0039] Although some preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments as well as all changes and modifications falling within the scope of the present application.

[0040] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of its inventive concept. Thus, if these modifications and variations to the present disclosure fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these changes and modifications.

Claims

1. A reticulated heterogeneous structure cast high-entropy alloy with good mechanical properties, characterized in that, Its alloy formula is CrFe x NiAl 0.28 Ti 0.12 , and the molar ratio of each element is Cr:Fe:Ni:Al:Ti = 1:x:1:0.28:0.12, where 0.9 ≤ x ≤ 1.

45.

2. The reticular heterogeneous structure cast high entropy alloy according to claim 1, characterized in that, Its alloy expression is CrFe x NiAl 0.28 Ti 0.12 , 1.0 ≤ x ≤ 1.

40.

3. The low-cost networked heterogeneous structure casting high-entropy alloy according to claim 1, characterized in that, Its alloy formula is CrFe x NiAl 0.28 Ti 0.12 , 1.1 ≤ x ≤ 1.

30.

4. The reticular heterogeneous structure cast high-entropy alloy according to claim 1, 2 or 3, characterized in that, It contains FCC phase and BCC phase, and part or all of the BCC phase is wrapped in a network structure composed of island-shaped and / or side-plate-shaped FCC phases.

5. The reticular heterogeneous structure cast high-entropy alloy according to claim 4, characterized in that, The BCC phase has a cellular structure, in which L21 nanoparticles are dispersed.

6. A preparation method of a reticular heterogeneous structure cast high-entropy alloy, characterized in that, It includes the following steps: (1) Configure the alloy smelting raw materials according to the element molar ratio described in Claim 1, and mix and melt them under vacuum or inert atmosphere to obtain an alloy liquid; (2) Repeatedly melt at least 4 times, and cast the obtained alloy liquid into shape to obtain the corresponding as-cast alloy ingot / component.

7. Application of the low-network heterogeneous structure cast high-entropy alloy described in Claim 1 in the manufacturing of chemical, energy, machinery, shipbuilding, marine or aerospace engineering equipment.

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