Netted biphase heterostructure casting high-entropy alloy and preparation and application thereof

Abstract

The invention relates to a reticular biphase 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. The CrFeNiAlSi series alloy is used as a matrix component, the alloy design is optimized by introducing the Ti element, and the CrFeNiAl0. 28Si0. 12-xTix as-cast high-entropy alloy is prepared by combining the vacuum arc melting and suction casting process. The mechanical property of the alloy is optimized by reasonably adding Ti into the CrFeNiAlSi alloy and regulating and controlling the content of Ti, meanwhile, the adverse effect brought by Ti is overcome or balanced, and the as-cast high-entropy alloy which has a heterogeneous phase structure between battens and has high strength and good plasticity is developed.

Description

Technical Field

[0001] The present invention relates to the technical field of high entropy alloys, and in particular to a network dual-phase heterogeneous structure casting high entropy alloy and its preparation and application. Background Art

[0002] High entropy alloys ( High-Entropy Alloys HEAs are a new material system that subverts traditional alloy design concepts. They are generally composed of five or more main elements in equimolar or near-equimolar proportions (the content of each element is between 5% and 35%). This multi-principal element design concept breaks the component limitations of traditional alloys and endows the material with a unique microstructure and excellent comprehensive performance through four core effects: high mixing entropy effect, lattice distortion effect, hysteresis diffusion effect, and "cocktail" effect.

[0003] Cast high-entropy alloys (HEAs) are those prepared directly through a melt-casting process. Compared to traditional cast alloys, cast HEAs typically exhibit finer dendritic structures, higher strength and hardness, and improved high-temperature stability. However, cast HEAs also have inherent defects, such as compositional segregation, shrinkage cavities and porosity, and high internal stresses. These defects often require subsequent complex heat treatment or plastic processing, such as forging, rolling, and heat treatment, to eliminate casting defects and obtain different microstructures and grain sizes, thereby adjusting the mechanical properties and corrosion resistance of the alloy. The process is often cumbersome, time-consuming, and labor-intensive.

[0004] By utilizing the metastable characteristics of high-entropy alloys and rationally designing their elemental composition, a complex heterogeneous structure can be obtained through its solid-state phase transformation during the cooling process after solidification. As a result, such alloys do not need to undergo complex mechanical-thermal treatment and can have excellent mechanical properties only in the cast state. By regulating this phase transformation process to optimize the complex heterogeneous structure, its comprehensive mechanical properties are expected to be further improved.

[0005] 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 an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0006] The study found that CrFeNiAl 0.28 Si 0.12-xA series of cast high-entropy alloys can undergo a BCC-FCC solid-state phase transformation during cooling after solidification to form a complex heterogeneous structure consisting of an FCC phase with a lath structure and a BCC phase containing dispersed nanoparticles between the laths. The inventors further discovered that the significant difference in mixing enthalpy between Ti and the various elements in the high-entropy alloys can alter the interactions between the alloying elements, stabilizing and diffusing each element, and regulating the complex heterogeneous structure of the high-entropy alloys. Increasing Ti content reduces the FCC phase content, resulting in a more ordered atomic arrangement. Si is evenly distributed throughout the phases, and low Si content contributes to solid solution strengthening in the high-entropy alloy system.

[0007] The inventors of this application have studied CrFeNiAl 0.28 Si 0.12 With an in-depth understanding of the mechanism of high-entropy alloys and combined with long-term accumulated research experience, we have optimized its mechanical properties by rationally doping the low-cost Ti element content to regulate the phase composition and microstructure, while overcoming or balancing the adverse effects it brings. We have developed a cast high-entropy alloy with a heterogeneous phase structure between laths and laths that has both high strength and good plasticity.

[0008] One aspect of the present disclosure provides a network dual-phase heterogeneous structure casting high entropy alloy, the alloy formula of which is CrFeNiAl 0.28 Si 0.12-x Ti x The molar ratio of each element is Cr:Fe:Ni:Al:Si:Ti = 1:1:1:0.28:0.12-x:x, and 0.01 <x<0.09。

[0009] In some embodiments of the present disclosure, 0.02≤x≤0.08.

[0010] In some embodiments of the present disclosure, x=0.08.

[0011] In some embodiments of the present disclosure, the high-entropy alloy contains an FCC phase and a BCC phase. The interlamellar BCC phase is encapsulated within the interlamellar FCC phase structure, forming a complex heterogeneous structure. FCC has relatively low strength but good plasticity, and is a soft phase. BCC has relatively high strength but less plasticity than FCC, and is a hard phase. This structure of the FCC soft phase encapsulating the BCC hard phase improves the overall mechanical properties of the alloy, achieving a good match and balance between strength and plasticity.

[0012] In some embodiments of the present disclosure, the BCC phase contains particles of the B2 ordered phase.

[0013] The B2 ordered phase can enhance the strength of the BCC phase through precipitation strengthening (precipitation strengthening is a well-known strengthening method).

[0014] According to a second aspect of the present disclosure, a method for preparing a network-shaped dual-phase heterogeneous structure cast high-entropy alloy having a cellular BCC phase and a lath-shaped FCC phase surrounding the cellular BCC phase is provided, comprising the following steps: (1) Alloy smelting raw materials are prepared according to the above-mentioned element molar ratios, mixed and smelted under vacuum or inert atmosphere to obtain alloy liquid; (2) Repeatedly smelt for at least 4 times, and cast the resulting alloy liquid into a corresponding cast alloy ingot / piece.

[0015] According to a third aspect of the present disclosure, the above-mentioned network heterostructure cast high entropy alloy is applied in the manufacture of ship, ocean or aerospace engineering equipment.

[0016] One or more technical solutions provided in the embodiments of the present disclosure have at least any of the following technical effects or advantages: 1. By adjusting CrFeNiAl 0.28 Si 0.12-x By optimizing the ratios of various elements in the system and rationally adding Ti, the alloy's strength, high-temperature stability, and wear resistance are significantly enhanced through controlling the phase structure, introducing strengthening phases, optimizing oxidation behavior (Ti and Al / Si synergistically promote the formation of a more stable Al-Ti-Si-O composite oxide film), refining the as-cast microstructure, and forming nanoclusters (such as Ti-Al-Si locally ordered regions). The resulting as-cast high-entropy alloy exhibits excellent mechanical properties (combining high yield strength with good ductility); for example, at room temperature (298K), the yield strength is 928-956 MPa, the ultimate tensile strength is 1480-1530 MPa, and the elongation at break is between 13.3% and 15.1%.

[0017] 2. Based on the CrFeNiAlSi system, an appropriate amount of Ti element is added. Compared with the CrFeNiAlSi system alloy without Ti element, the obtained alloy material not only has high strength characteristics, but also can maintain good plasticity under high strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is the cast X-ray diffraction pattern (XRD) of the alloy materials obtained in Examples 1 to 4 of the present application.

[0019] Figure 2 The SEM morphologies of the alloy materials obtained in Examples 1 to 4 of the present application are shown.

[0020] Figure 3 1 and 2 are the tensile stress-strain curves of the alloy materials obtained in Examples 1 to 4 of the present application.

[0021] Figure 4The yield strength (YS), ultimate tensile strength (UTS) and tensile plasticity (ε p ) change trend chart.

[0022] Figure 5 TEM and elemental analysis diagram of Ti0.02 in the examples of this application.

[0023] Figure 6 TEM and elemental analysis diagram of Ti0.08 in the examples of this application.

[0024] Figure 7 This is a trend diagram of Ti content-yield strength and tensile strength in the examples of this application.

[0025] Figure 8 This is a trend diagram of Ti content-uniform elongation in the examples of this application. DETAILED DESCRIPTION

[0026] In order to better understand the technical solution of the present application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0027] Unless otherwise specified, the instruments and equipment involved in the following examples are all conventional instruments and equipment; the raw materials involved are all commercially available conventional raw materials, unless otherwise specified; the preparation methods and detection methods involved are all conventional methods, unless otherwise specified.

[0028] Example 1: High Entropy Alloy CrFeNiAl 0.28 Si 0.1 Ti 0.02 Preparation According to CrFeNiAl 0.28 Si 0.1 Ti 0.02 The proportion of elements in the alloy, with a purity greater than 99.9wt% of elements (chromium, iron, nickel, aluminum, silicon, titanium) as raw materials, was prepared by arc melting in Ar atmosphere with a nominal composition of CrFeNiAl 0.28 Si 0.1 Ti 0.02 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 Ti0.02).

[0029] A dog-bone-shaped flat specimen of 10 mm × 2 mm × 1.5 mm was cut from a rectangular rod sample. Stretching was performed at room temperature using a screw-driven Suns UTM 5105 testing machine at a deformation rate of 0.1 mm / min. The XRD results are shown in Table 1. Figure 1 , SEM morphology see Figure 2 , TEM and elemental analysis see Figure 5 Its yield strength, tensile strength and uniform elongation are shown in Table 1.

[0030] Example 2: High Entropy Alloy CrFeNiAl 0.28 Si 0.08 Ti 0.04 Preparation According to CrFeNiAl 0.28 Si 0.08 Ti 0.04 The proportion of elements in the alloy, with a purity greater than 99.9wt% of elements (chromium, iron, nickel, aluminum, silicon and titanium) as raw materials, was prepared by arc melting in Ar atmosphere with a nominal composition of CrFeNiAl 0.28 Si 0.08 Ti 0.04 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 Ti0.04).

[0031] A dog-bone-shaped flat specimen of 10 mm × 2 mm × 1.5 mm was cut from a rectangular rod sample. Stretching was performed at room temperature using a screw-driven Suns UTM 5105 testing machine at a deformation rate of 0.1 mm / min. The XRD results are shown in Table 1. Figure 1 , SEM morphology see Figure 2 Its yield strength, tensile strength and uniform elongation are shown in Table 1.

[0032] Example 3: High Entropy Alloy CrFeNiAl 0.28 Si 0.06 Ti 0.06 Preparation According to CrFeNiAl 0.28 Si 0.06 Ti 0.06 The proportion of elements in the alloy, with a purity greater than 99.9wt% of elements (chromium, iron, nickel, aluminum, silicon and titanium) as raw materials, was prepared by arc melting in Ar atmosphere with a nominal composition of CrFeNiAl 0.28 Si 0.06 Ti 0.06 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 Ti0.06).

[0033] A dog-bone-shaped flat specimen of 10 mm × 2 mm × 1.5 mm was cut from a rectangular rod sample. Stretching was performed at room temperature using a screw-driven Suns UTM 5105 testing machine at a deformation rate of 0.1 mm / min. The XRD results are shown in Table 1. Figure 1 , SEM morphology see Figure 2 Its yield strength, tensile strength and uniform elongation are shown in Table 1.

[0034] Example 4: High Entropy Alloy CrFeNiAl 0.28 Si 0.04 Ti 0.08 Preparation According to CrFeNiAl 0.28 Si 0.04 Ti 0.08 The proportion of elements in the alloy, with a purity greater than 99.9wt% of elements (chromium, iron, nickel, aluminum, silicon and titanium) as raw materials, was prepared by arc melting in Ar atmosphere with a nominal composition of CrFeNiAl 0.28 Si 0.04 Ti 0.08 All the ingots were remelted 5 times under electromagnetic stirring to ensure uniformity and suction cast into 10×10×50 mm 3 The XRD results of the rectangular rod alloy sample (named Ti0.08) are shown in Figure 2. Figure 1 , SEM morphology see Figure 2 Its yield strength, tensile strength and uniform elongation are shown in Table 1.

[0035] A dog-bone-shaped flat specimen of 10 mm × 2 mm × 1.5 mm was cut from a rectangular rod sample. Stretching was performed at room temperature using a screw-driven Suns UTM 5105 testing machine at a deformation rate of 0.1 mm / min. The XRD results are shown in Table 1. Figure 1 , SEM morphology see Figure 2 , TEM and elemental analysis see Figure 6 Its yield strength, tensile strength and uniform elongation are shown in Table 1.

[0036] Table 1 Yield strength (YS), tensile strength (UTS) and uniform elongation (ε p )index .

[0037] from Figure 1 It can be seen that with the continuous increase of Ti element content, the diffraction peak intensity of the BCC phase has an upward trend, and the diffraction peak intensity of the FCC phase continues to decrease.

[0038] From the SEM images of Examples 1 to 4 ( Figure 2 ) shows that as Ti content increases, the microstructure of the as-cast high-entropy alloy transforms from the FCC phase and BCC cellular structure distributed between BCC cellular regions in Ti0.02 and Ti0.04 to the FCC network and BCC cellular structure in Ti0.06 and Ti0.08, containing dispersed nanoparticles. As Ti content increases, the FCC lath casting becomes coarser, with the presence of FCC gradually concentrating from the interior of the BCC unit cell to the grain boundaries of the BCC unit cell, ultimately forming the FCC network structure in Ti0.08.

[0039] The stress-strain curves of Examples 1 to 4 ( Figure 3 ) and Table 1, it can be seen that the yield strength of Example 1 is 604MPa, the ultimate tensile strength is 1265MPa, and the elongation is 23.90%. The yield strength of Example 2 is 694MPa, the ultimate tensile strength is 1318MPa, and the elongation is 18.50%. The yield strength of Example 3 is 760MPa, the ultimate tensile strength is 1414MPa, and the elongation is 14.70%. The yield strength of Example 4 is 942MPa, the ultimate tensile strength is 1505MPa, and the elongation is 11.20%. As can be seen from Table 1, when the Ti content is 0.08, the alloy material performance is the best, its yield strength can reach 942MPa, the ultimate tensile strength can reach 1505MPa, and the comprehensive mechanical properties are excellent. The elongation of the alloy material can reach 11.20%.

[0040] from Figure 4 It can be seen that the yield strength (YS), ultimate tensile strength (UTS) and tensile plasticity (ε p ) trend chart. This cast high-entropy alloy has excellent strength properties. The combination of the FCC network structure and the BCC cellular structure formed by adding an appropriate amount of Ti has a good synergistic effect, which is beneficial for stress distribution and reduces stress concentration, and can maintain good plasticity at high strength.

[0041] from Figure 5 and Figure 6 The TEM and elemental analysis diagrams shown in the figure show that the addition of Ti element affects the phase transformation behavior of the cast high-entropy alloy; when the Ti molar number is 0.02, FCC and BCC are connected in a similar way to the bainite transformation to produce FCC phase inside the BCC parent phase unit cell, and the nanoparticles have a B2 structure; as the Ti molar number increases to 0.08, the alloy undergoes a solid-state phase transformation, BCC is preferentially generated as the parent phase, FCC precipitates from the grain boundary 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 strength of the alloy 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 700MPa, 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 、 Figure 8 It can be seen that when the molar number of Ti in the alloy system is greater than 0.06, the yield strength and ultimate tensile strength meet the requirements; therefore, considering the satisfaction of the above index requirements, the preferred molar number of Ti in the alloy system is 0.06~0.08.

[0043] Although some preferred embodiments of the present application have been described, those skilled in the art may make additional 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.

[0044] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the inventive concept. Thus, if such modifications and variations of the present disclosure fall within the scope of the claims and their equivalents, the present application is intended to include such modifications and variations.

Claims

1. A network dual-phase heterogeneous structure casting high entropy alloy, characterized in that: Its alloy expression is CrFeNiAl 0.28 Si 0.12-x Ti x The molar ratio of each element is Cr: Fe: Ni: Al: Si: Ti = 1: 1: 1: 0.28: 0.12-x: x, and 0.01 <x<0.09。 2. The network dual-phase heterogeneous structure casting high entropy alloy according to claim 1, characterized in that: Its alloy expression is CrFeNiAl 0.28 Si 0.12-x Ti x , 0.02≤x≤0.

08.

3. The network dual-phase heterogeneous structure casting high entropy alloy according to claim 1, characterized in that: Its alloy expression is CrFeNiAl 0.28 Si 0.12-x Ti x , x=0.

08.

4. The network dual-phase heterogeneous structure cast high entropy alloy according to claim 1, 2 or 3, characterized in that: It contains an FCC phase and a BCC phase, wherein the BCC phase is wrapped in a continuous or discontinuous network structure composed of the FCC phase.

5. The network dual-phase heterogeneous structure cast high entropy alloy according to claim 1, 2 or 3, characterized in that: It contains a BCC phase and a lath-shaped FCC phase, wherein the BCC phase is distributed between the laths of the FCC phase.

6. The network dual-phase heterogeneous structure casting high entropy alloy according to claim 5, characterized in that: The BCC phase contains particles of the B2 ordered phase.

7. A method for preparing a network dual-phase heterogeneous structure casting high entropy alloy, characterized in that: The following steps are involved: (1) preparing the alloy smelting raw materials according to the molar ratio of the elements as claimed in claim 1, mixing and smelting them under vacuum or inert atmosphere to obtain a molten alloy; (2) Repeatedly smelt the alloy for at least four times, and cast the resulting alloy liquid into a corresponding cast alloy ingot.

8. Use of the network dual-phase heterogeneous structure cast high entropy alloy according to claim 1 in the manufacture of shipbuilding, marine or aerospace engineering equipment.

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