Mesh heterostructure casting high-entropy alloy and preparation and application thereof

Abstract

The invention relates to a reticular heterostructure cast high-entropy alloy as well as preparation and application thereof, and aims to solve the technical problems of high production cost and long period caused by dependence on introduction of high-cost elements or a complex process in the conventional high-entropy alloy. According to the preparation method, CrFeNiAl0. 28 is taken as a matrix component, the alloy design is optimized by introducing a Ti element, and the CrFeNiAl0. 28Tix as-cast high-entropy alloy is prepared by combining a vacuum arc melting and suction casting process. According to the invention, the mechanical property of the alloy is optimized by reasonably adding Ti into the CrFeNiAl0.28 series alloy and regulating and controlling the content of Ti, and meanwhile, the adverse effect brought by Ti is overcome or balanced, and the reticular bionic heterostructure casting high-entropy alloy with high strength, good plasticity and lower preparation cost is developed.

Description

Technical Field

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

[0002] High-Entropy Alloys (HEAs) are advanced alloy materials composed of 5 or more principal elements (each atomic percentage is 5% - 35%). 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. Traditional high-entropy alloys usually form a multi-phase structure during the cooling process through solid-state phase transformation, thereby obtaining excellent as-cast properties. For example, the as-cast high-entropy alloy of the CrFeNiAl 0.28 system shows relatively high tensile strength (such as > 500 MPa) and good ductility (fracture strain > 30%) at room temperature, and does not rely on expensive elements such as Co 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 material property requirements in the engineering field, how to further optimize the strength while maintaining sufficient plasticity has become a key challenge in the composition design of high-entropy alloys. In the prior art, although the performance can be improved by adding high-cost elements (such as Co) or introducing complex processes, it will lead to an increase in cost and an extension of the production cycle, restricting their 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 has been found through research that the distribution and content of the FCC (face-centered cubic) and BCC (body-centered cubic) phases in the CrFeNiAl-based high-entropy alloy have a significant impact on its mechanical properties. The FCC structure usually exhibits high plasticity and toughness but low strength, while 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 an in-depth understanding of the mechanism of the CrFeNiAl-based high-entropy alloy and combined with long-term accumulated research experience, the inventors of the present application developed a cast high-entropy alloy with a reticular heterogeneous phase structure having both high strength and good plasticity by reasonably doping low-cost Ti elements therein to regulate the phase composition and microstructure, and further optimizing its mechanical properties while overcoming or balancing the adverse effects brought by them.

[0006] One aspect of the present disclosure provides a reticulated heterogeneous structure cast high-entropy alloy with an alloy formula of CrFeNiAl 0.28 Ti x , and the molar ratio of each element is Cr:Fe:Ni:Al:Ti = 1:1:1:0.28:x, where 0 < x < 0.16.

[0007] In some embodiments of the present disclosure, 0.04 ≤ x ≤ 0.15.

[0008] In some embodiments of the present disclosure, 0.06 ≤ x ≤ 0.14.

[0009] In some embodiments of the present disclosure, x = 0.12.

[0010] In some embodiments of the present disclosure, the high-entropy alloy contains an FCC phase and a BCC phase, and the BCC phase is wrapped in a continuous or discontinuous reticulated structure composed of the FCC phase. Among them, the strength of the FCC is relatively low and the plasticity is relatively good, belonging to the soft phase; the strength of the BCC is relatively high and the plasticity is not as good as that of the FCC, belonging to the hard phase; the structure in which the FCC soft phase wraps the BCC hard phase is conducive to improving the overall mechanical properties of the alloy, enabling good matching of strength and plasticity (taking both strength and plasticity into account).

[0011] In some embodiments of the present disclosure, the BCC phase contains particles of the B2 ordered phase. Among them, the B2 ordered phase can further improve the strength of the BCC phase through precipitation strengthening.

[0012] According to the second aspect of the present disclosure, a method for preparing a reticulated heterogeneous structure cast high-entropy alloy is provided, including the following steps: (1) Configure each smelting raw material according to the above element molar ratio, and mix and melt in a vacuum or inert atmosphere to obtain an alloy liquid; (2) The alloy is repeatedly melted at least 4 times, and the obtained alloy liquid is cast into shape to obtain a corresponding as-cast alloy ingot / component.

[0013] According to the third aspect of the present disclosure, the above reticulated heterogeneous structure cast high-entropy alloy is applied to the manufacture of ships, marine or aerospace engineering equipment.

[0014] 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 adjusting the proportion of each element in the CrFeNiAl system and reasonably adding the Ti element, an as-cast high-entropy alloy with good mechanical properties (both high yield strength and good plasticity) is developed; the yield strength of the alloy at room temperature (298K) is 1243 - 1297 MPa, the ultimate tensile strength is 1556 - 1640 MPa, and the fracture elongation is between 11.4% and 13.0%.

[0015] 2. Based on the CrFeNiAl system, by adding an appropriate amount of Ti element, compared with the CrFeNiAl system alloy without Ti element, the obtained alloy material not only has high strength characteristics, but also can maintain good plasticity under high strength. Description of the Drawings

[0016] Figure 1 It is the as-cast X-ray diffraction pattern (XRD) of the alloy materials obtained in Examples 1 to 4 of this application.

[0017] Figure 2 It is the SEM morphology of the alloy materials obtained in Examples 1 to 4 of this application.

[0018] Figure 3 It is the tensile stress-strain curve of the alloy materials obtained in Examples 1 to 5 of this application.

[0019] Figure 4 It is the trend chart of the yield strength (YS), ultimate tensile strength (UTS), and uniform elongation (ε) of the as-cast high-entropy alloy in the examples of this application.

[0020] Figure 5 It is the TEM and elemental analysis diagram of Ti0 in the examples of this application.

[0021] Figure 6 It is the TEM and elemental analysis diagram of Ti0.12 in the examples of this application.

[0022] Figure 7 It is the trend chart of Ti content - yield strength and tensile strength in the examples of this application.

[0023] Figure 8 It is the trend chart of Ti content - uniform elongation in the examples of this application. Detailed Embodiments

[0024] In order to better understand the technical solution of this application, the above technical solution will be described in detail below in combination with the drawings of the specification and specific embodiments.

[0025] In the following examples, 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.

[0026] Example 1. High-entropy alloy CrFeNiAl 0.28 Preparation of Ti0 According to CrFeNiAl 0.28The elemental ratios in the Ti0 alloy. Using elements with a purity greater than 99.9 wt% (chromium, iron, nickel, and aluminum) as raw materials, an alloy ingot with a nominal composition of CrFeNiAl 0.28 Ti0 was prepared by arc melting in an Ar atmosphere. The alloy ingot was remelted 5 times under electromagnetic stirring to ensure uniformity, and then suction cast into a cuboid bar-shaped alloy specimen with dimensions of 10×10×50 mm 3 (named Ti0).

[0027] Flat specimens with a dog-bone shape of 10 mm×2 mm×1.5 mm were cut from the cuboid bar-shaped specimens. Tensile tests were carried out at room temperature using a screw-driven Suns UTM 5105 testing machine at 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 5 , and the yield strength, tensile strength, and uniform elongation indexes are shown in Table 1.

[0028] Example 2. High-entropy alloy CrFeNiAl 0.28 Ti 0.04 Preparation According to the elemental ratios in the CrFeNiAl 0.28 Ti 0.04 alloy, using elements with a purity greater than 99.9 wt% (chromium, iron, nickel, aluminum, and titanium) as raw materials, an alloy ingot with a nominal composition of CrFeNiAl 0.28 Ti 0.04 was prepared by arc melting in an Ar atmosphere. The alloy ingot was remelted 5 times under electromagnetic stirring to ensure uniformity, and then suction cast into a cuboid bar-shaped alloy specimen with dimensions of 10×10×50 mm 3 (named Ti0.04).

[0029] Flat specimens with a dog-bone shape of 10 mm×2 mm×1.5 mm were cut from the cuboid bar-shaped specimens. Tensile tests were carried out at room temperature using a screw-driven Suns UTM 5105 testing machine at 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 , and the yield strength, tensile strength, and uniform elongation indexes are shown in Table 1.

[0030] Example 3. High-entropy alloy CrFeNiAl 0.28 Ti 0.08 Preparation According to the CrFeNiAl 0.28 Ti 0.08The element ratios in the alloy. Using elements with a purity greater than 99.9 wt% (chromium, iron, nickel, aluminum, and titanium) as raw materials, an alloy ingot with a nominal composition of CrFeNiAl 0.28 Ti 0.08 was prepared by arc melting in an Ar atmosphere. The alloy ingot was remelted at least 5 times under electromagnetic stirring to ensure uniformity, and then suction-cast into a cuboid bar-shaped alloy specimen with dimensions of 10×10×50 mm 3 (named Ti0.08).

[0031] Flat specimens with a dog-bone shape of 10 mm×2 mm×1.5 mm were cut from the cuboid bar-shaped specimen. Tensile tests were carried out at room temperature using a screw-driven Suns UTM 5105 testing machine at 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 , and the yield strength, tensile strength, and uniform elongation indexes are shown in Table 1.

[0032] Example 4. Preparation of high-entropy alloy CrFeNiAl 0.28 Ti 0.12 Preparation According to the element ratios in the CrFeNiAl 0.28 Ti 0.12 alloy, using elements with a purity greater than 99.9 wt% (chromium, iron, nickel, aluminum, and titanium) as raw materials, an alloy ingot with a nominal composition of CrFeNiAl 0.28 Ti 0.12 was prepared by arc melting in an Ar atmosphere. The alloy ingot was remelted 5 times under electromagnetic stirring to ensure uniformity, and then suction-cast into a cuboid bar-shaped alloy specimen with dimensions of 10×10×50 mm 3 (named Ti0.12).

[0033] Flat specimens with a dog-bone shape of 10 mm×2 mm×1.5 mm were cut from the cuboid bar-shaped specimen. Tensile tests were carried out at room temperature using a screw-driven Suns UTM 5105 testing machine at 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.

[0034] Example 5. Preparation of high-entropy alloy CrFeNiAl 0.28 Ti 0.16 Preparation According to CrFeNiAl 0.28 Ti 0.16The element ratios in the alloy were prepared by arc melting in an Ar atmosphere using elements (chromium, iron, nickel, aluminum, and titanium) with a purity greater than 99.9 wt% as raw materials to obtain an alloy ingot with a nominal composition of CrFeNiAl 0.28 Ti 0.16 The alloy ingot was remelted 5 times under electromagnetic stirring to ensure uniformity and then suction-cast into a rectangular bar-shaped alloy specimen with dimensions of 10×10×50 mm 3 (named Ti0.16).

[0035] Flat specimens with a dog-bone shape of 10 mm×2 mm×1.5 mm were cut from the rectangular bar-shaped specimens. Tensile tests were carried out at a deformation rate of 0.1 mm / min at room temperature using a screw-driven Suns UTM 5105 testing machine. After testing, the XRD results are shown in Figure 1 , the SEM morphology is shown in Figure 2 , and the yield strength, tensile strength, and uniform elongation indexes are shown in Table 1.

[0036] Table 1 Yield strength (YS), tensile strength (UTS), and uniform elongation (ε) indexes of each alloy .

[0037] It can be seen from Figure 1 that as the content of Ti element increases continuously, the intensity of the BCC phase diffraction peak shows an upward trend, while the intensity of the FCC phase diffraction peak decreases continuously.

[0038] It can be seen from the SEM images of Examples 1 to 4 ( Figure 2 ) that as the Ti content increases, the microstructure of the as-cast high-entropy alloy changes from the FCC dendritic and BCC cellular structures of Ti0 and Ti0.04 to the FCC network and BCC cellular structures of Ti0.08 and Ti0.12, and all contain uniformly distributed nanoparticles.

[0039] From the stress-strain curve graphs of Examples 1 to 5 ( Figure 3) and Table 1, it can be seen that the yield strength of the first embodiment is 475MPa, the ultimate tensile strength is 885MPa, and the elongation is 35.10%. The yield strength of the second embodiment is 709MPa, the ultimate tensile strength is 1114MPa, and the elongation is 29.10%. The yield strength of the third embodiment is 969MPa, the ultimate tensile strength is 1375MPa, and the elongation is 18.10%. The yield strength of the fourth embodiment is 1270MPa, the ultimate tensile strength is 1598MPa, and the elongation is 12.20%. Since the fracture mode of the fifth embodiment is brittle fracture, the fracture occurs before yielding, and the fracture strength is 1367MPa. It can be seen from Table 1 that when the Ti content is 0.12, the alloy material has the best performance, and its yield strength can reach 1297MPa, the ultimate tensile strength can reach 1640MPa, and the comprehensive mechanical properties are excellent. The elongation of the alloy material can reach 13.0%.

[0040] from Figure 4 It can be seen from the graph that the yield strength (YS), ultimate tensile strength (UTS) and uniform elongation (ε) of this series of cast high entropy alloys have excellent strength characteristics, and the combination of FCC network structure and BCC cellular structure formed by adding appropriate amount of Ti element has good synergy, which is conducive to stress distribution and reduces stress concentration, and can maintain good plasticity under high strength.

[0041] From TEM and elemental analysis ( Figure 5 , Figure 6 ) It can be seen that the addition of Ti element affects the phase transformation behavior of the cast high-entropy alloy; when the Ti content is 0, FCC and BCC phases are directly formed through liquid-solid transformation, and FCC precipitates preferentially, and the nanoparticles have a B2 structure; with the increase of Ti content, the alloy undergoes a solid-state phase transformation, BCC is preferentially generated as the parent phase, FCC precipitates from the grain boundaries and extends inward, and the nanoparticles are transformed into an L21 structure; at the same time, L21 blocks containing BCC laths are generated in the FCC network structure, forming a complex heterogeneous structure, which greatly improves the alloy strength while still maintaining the plasticity required for the casting alloy.

[0042] Generally speaking, the yield strength of the new generation of high-strength steel needs to be greater than 800MPa, the ultimate tensile strength needs to be greater than 1200MPa and the elongation needs to be greater than 8%. According to this standard, and referring to Figure 7 It can be seen that when the molar proportion of Ti is greater than 0.06, the yield strength and ultimate tensile strength meet the requirements; Figure 8 It can be seen that the molar proportion of Ti cannot be higher than 0.14; therefore, considering the above index requirements, the proportion of Ti is preferably 0.06 to 0.14.

[0043] Although some preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present application.

[0044] Obviously, those skilled in the art can make various changes and modifications to the present disclosure 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 this application and their equivalent technologies, this application is also intended to include these modifications and variations.

Claims

1. A reticular heterogeneous structure cast high-entropy alloy, characterized in that, Its alloy formula is CrFeNiAl 0.28 Ti x , and the molar ratio of each element is Cr:Fe:Ni:Al:Ti = 1:1:1:0.28:x, where 0 < x < 0.

16.

2. The reticular heterogeneous structure cast high-entropy alloy according to claim 1, characterized in that, Its alloy formula is CrFeNiAl 0.28 Ti x , 0.04 ≤ x ≤ 0.15 3. The reticular heterogeneous structure cast high-entropy alloy according to claim 1, characterized in that Its alloy formula is CrFeNiAl 0.28 Ti x , 0.06 ≤ x ≤ 0.14 4. The reticular heterogeneous structure cast high-entropy alloy according to claim 1, characterized in that, Its alloy formula is CrFeNiAl 0.28 Ti x , where x = 0.12 5. The reticulated heterogeneous structure cast high-entropy alloy according to claim 1, 2, 3 or 4, characterized in that, It contains FCC phase and BCC phase, and the BCC phase is wrapped in a continuous or discontinuous network structure composed of FCC phase.

6. The reticular heterogeneous structure cast high-entropy alloy according to claim 5, characterized in that, The BCC phase contains particles of B2 ordered phase.

7. A preparation method of a reticulated 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 alloy liquid; (2) The alloy is repeatedly melted at least 4 times, and the obtained alloy liquid is cast into shape to obtain the corresponding as-cast alloy ingot / component.

8. Application of the reticular heterogeneous structure cast high-entropy alloy described in Claim 1 in the manufacture of ships, marine or aerospace engineering equipment.

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