A nano-precipitated phase-enhanced multiphase Fe 5-x Cr x NiAl 0.3 Ti 0.3 High-entropy alloys

Abstract

The present application relates to the field of nano-precipitate strengthening multiphase high-entropy alloy, in particular to a nano-precipitate strengthening multiphase Fe 5‑ x Cr x NiAl 0.3 Ti 0.3 High-entropy alloy. The alloy composition range is changed according to the following principles: Fe 5‑x Cr x NiAl 0.3 Ti 0.3 (molar ratio), x = 1.13, 1.25, 1.36, 1.47 and 1.67. The performance index is: tensile yield strength is 608 MPa to 1248 MPa, tensile strength is 958 MPa to 1295 MPa, and total elongation at break is 1.1% to 20.6%. The present application changes the ratio of Cr / Fe to control the relative content of disordered face-centered cubic phase (FCC) and disordered body-centered cubic matrix phase and the nano-scale ordered L21-Ni2AlTi phase (BCC / L21) precipitated thereon, and at the same time, a large amount of L21 nano-precipitate phase is obtained in the BCC / L21 region; in addition, with the increase of the content of Cr element, the morphology of FCC phase evolves from dendritic to equiaxed grain boundary shape, and the grain of the alloy is refined; these two factors result in that the microstructure and properties of the Fe 5‑x Cr x NiAl 0.3 Ti 0.3 High-entropy alloy can be significantly regulated by changing the ratio of Cr / Fe.

Description

Technical Field

[0001] This invention relates to the field of nano-precipitated phase-reinforced multiphase high-entropy alloys, specifically to a nano-precipitated phase-reinforced multiphase Fe alloy. 5-x Cr x NiAl 0.3 Ti 0.3 High-entropy alloys. Background Technology

[0002] High-entropy alloys are a new type of metallic material formed by alloying multiple elements in equiatomic or near-equiatomic ratios. Unlike traditional alloy design concepts based on mono- or binary elements, high-entropy alloys possess unique atomic structure characteristics due to their revolutionary alloy design philosophy, resulting in many excellent mechanical, physical, and chemical properties. However, their microstructure and properties still need improvement. As is well known, high-entropy alloys can be broadly classified into three categories based on their crystal structure: FCC, BCC, and HCP. BCC and HCP high-entropy alloys typically exhibit high strength and have great potential for structural applications. However, these high-entropy alloys usually exhibit poor plasticity, which severely limits their applications. FCC high-entropy alloys possess high plasticity. However, the low room-temperature yield strength of FCC high-entropy alloys seriously hinders their development and application as structural materials. Based on this, researchers have developed high-entropy alloys with an FCC+BCC structure, but this usually introduces a new problem of strength-plasticity trade-offs.

[0003] To improve the overall performance of alloys, scholars from various countries have proposed a variety of strategies to minimize the strength-plasticity trade-off. For example: (1) metastable engineering strategy to prepare high-entropy alloys with nanostructures; (2) controlling the nickel content in the alloy to prepare AlCoCrFeNi2 with a eutectic structure; (3) designing a series of Al2 (Ni, Co, Fe, Cr) with different Ni, Co, Fe and Cr contents. 14 It was found that by controlling the content of the above elements, a microstructure with uniform B2 cubic particle distribution can be obtained, thereby significantly improving the overall mechanical properties of the alloy.

[0004] In recent years, researchers have conducted extensive studies on high-entropy alloys strengthened by nanoprecipitates. Compared with other strengthening methods, nanoprecipitate strengthening can significantly improve the overall mechanical properties of materials. However, most of these high-entropy alloys contain expensive Co, resulting in high manufacturing costs and limiting their practical application. Therefore, considering the manufacturing cost, developing Co-free high-entropy alloys with excellent mechanical properties through nanoprecipitate strengthening has significant technical and application value. Summary of the Invention

[0005] The purpose of this invention is to provide a nano-precipitated phase-enhanced multiphase Fe5-x Cr x NiAl 0.3 Ti 0.3 High-entropy alloys are obtained by controlling the microstructure of these alloys through the Cr / Fe ratio, thereby achieving Fe-Cr-Ni-Al-Ti high-entropy alloys with excellent mechanical properties.

[0006] The technical solution described in this invention is as follows:

[0007] A nano-precipitated phase-enhanced multiphase Fe 5-x Cr x NiAl 0.3 Ti 0.3 High entropy alloys, by molar ratio, the alloy composition follows Fe 5-x Cr x NiAl 0.3 Ti 0.3 (Molar ratio), x = 1.13, 1.25, 1.36, 1.47 and 1.67, and represented as C13, C25, C36, C47 and C67 respectively.

[0008] The nano-precipitated phase-enhanced multiphase Fe 5-x Cr x NiAl 0.3 Ti 0.3 The high-entropy alloy has three phases: a disordered FCC phase, a disordered BCC matrix phase, and a nano-ordered L21-Ni2AlTi phase precipitated on the BCC matrix phase. The L21-Ni2AlTi nano-precipitates have nucleation capabilities, and a large number of dispersed spherical L21-Ni2AlTi nano-precipitates are precipitated in the alloy cast by the copper mold.

[0009] The nano-precipitated phase-enhanced multiphase Fe 5-x Cr x NiAl 0.3 Ti 0.3 In high-entropy alloys, as the Cr content increases (i.e. Cr replaces Fe), the volume fraction of the BCC / L21-Ni2AlTi phase increases, the morphology of the FCC phase changes from dendritic to equiaxed grain boundary shape, and the grains of the alloy are refined.

[0010] The nano-precipitated phase-enhanced multiphase Fe 5-x Cr x NiAl 0.3 Ti 0.3High-entropy alloys exhibit significant changes in tensile mechanical properties through the addition of chromium (Cr). Yield strength: C13 alloy 608 MPa, C25 alloy 777 MPa, C36 alloy 1071 MPa, C47 alloy 1163 MPa, C67 alloy 1248 MPa; Tensile strength: C13 alloy 958 MPa, C25 alloy 1142 MPa, C36 alloy 1260 MPa, C47 alloy 1342 MPa, C67 alloy 1295 MPa; Total elongation at break: C13 alloy 20.6%, C25 alloy 9.5%, C36 alloy 3.1%, C47 alloy 2.2%, C67 alloy 1.1%. The addition of Cr reduces the tensile plasticity of these high-entropy alloys while significantly enhancing their strength, thus improving their overall performance, as seen in alloys C13 and C25.

[0011] The nano-precipitated phase-enhanced multiphase Fe 5-x Cr x NiAl 0.3 Ti 0.3 The microstructure and mechanical properties of high-entropy alloys are controlled by changing the Cr / Fe ratio, including: (1) adjusting the content of FCC phase and BCC / L21-Ni2AlTi phase by changing the Cr / Fe ratio; (2) increasing the Cr / Fe ratio causes the morphology of the FCC phase to evolve from dendritic to equiaxed grain boundary shape, and the grains of the alloy are refined. The changes in microstructure lead to the control of the corresponding tensile mechanical properties of the high-entropy alloy.

[0012] The present invention describes a method for enhancing multiphase Fe by controlling the nano-precipitated phase through changing the Cr / Fe ratio. 5-x Cr x NiAl 0.3 Ti 0.3 The principle of high-entropy alloys is as follows:

[0013] Modifying the Cr / Fe ratio to regulate the nano-precipitation phase enhancement of multiphase Fe 5-x Cr x NiAl 0.3 Ti 0.3 The principles underlying the microstructure and properties of high-entropy alloys include: increasing the Cr / Fe ratio increases the content of the BCC / L21-Ni2AlTi phase and decreases the content of the FCC phase, while simultaneously obtaining a large number of relatively uniformly dispersed L21-Ni2AlTi nano-precipitates in the BCC / L21 region, thus affecting the alloy's properties; furthermore, with the increase of the Cr / Fe ratio, the morphology of the FCC phase evolves from dendritic to equiaxed grain boundary shape, and the alloy grains are refined, further influencing the alloy's properties. These two principles are described in detail below:

[0014] (i) Increasing the Cr / Fe ratio increases the content of the BCC / L21-Ni2AlTi phase and decreases the content of the FCC phase in the alloy.

[0015] The VEC criterion (see reference: Guo S, Ng C, Lu J, et al., Effect of valence electronconcention on stability of offcc or bcc phase in high-entropy alloys[J]. Journal of Applied Physics, 2011, 109(10): 103505) plays an important role in the research of high-entropy alloys. This criterion has important guiding significance for the phase formation and phase transformation of alloys. The definition of VEC is as follows:

[0016]

[0017] In the formula, c i Let (VEC) represent the atomic percentage of the i-th element. i Let VEC (valence electron concentration) be the value of the i-th element. The required parameters in the formula are shown in Table 1. The valence electron concentration of the high-entropy alloy was calculated according to formula (1), and the obtained valence electron concentration values ​​are shown in Table 2. The results show that as the Cr content increases (the Cr / Fe ratio increases), the VEC of the alloy gradually decreases. According to the VEC criterion, when the VEC value is high, the FCC-related phase is more stable; when the VEC value is low, the BCC-like related phase is more stable. According to the above analysis, the increase of Cr content reduces the VEC of the alloy, resulting in an increase in the BCC / L21-Ni2AlTi phase content and a decrease in the FCC phase content.

[0018] Table 1 shows the valence electron concentrations of each component element in the high-entropy alloy.

[0019] Element Fe Cr Ni Al Ti VEC 8 6 10 3 4

[0020] Table 2 shows the VEC values ​​of the high-entropy alloys.

[0021] Alloys C13 C25 C36 C47 C67 VEC 7.55 7.52 7.48 7.45 7.39

[0022] (ii) The increase in the Cr / Fe ratio causes the FCC phase morphology of the alloy to evolve from dendritic to equiaxed grain boundary shape, and the grains are refined.

[0023] As described above, in the high-entropy alloys, with increasing Cr content, the volume fraction of the BCC / L21-Ni2AlTi phase increases, while the FCC phase decreases, indicating a competitive relationship between the BCC / L21-Ni2AlTi and FCC phases. In alloys C13 and C25, a relatively large amount of FCC phase exists. Since the Al and Ti content in the FCC phase is low, resulting in fewer atomic clusters in the liquid state, it is easier to form FCC columnar crystals. In alloy C36, both columnar and equiaxed crystals exist, while in alloy C47, equiaxed crystals are predominantly present. The grains of these two alloys consist of both BCC and L21 phases, with the grain boundaries composed of the FCC phase. Therefore, due to the decrease in the volume fraction of the FCC phase, it is difficult for FCC columnar crystals to form, and the grain shape of these two alloys is controlled by the growth of the BCC and L21 phases. The reason for the formation of equiaxed crystals is that the volume fraction of the FCC phase in the two alloys is small, making it difficult for columnar crystals to form; and in the BCC / L21-Ni2AlTi phase region, Al and Ti form strong covalent bonds with the surrounding Fe, Cr, and Ni atoms, generating atomic clusters. That is, in the liquid state, this region contains a large number of atomic clusters, resulting in a high nucleation rate, so it is easy to form equiaxed crystals.

[0024] Comparing the C47 and C67 alloys, the grain size decreases again. This is because the C67 alloy lacks the FCC phase, which further increases the nucleation and growth area in the liquid phase, thus increasing the probability of nucleation. A comparison of the microstructures of the high-entropy alloys reveals that the particle size of the L21 nano-precipitate phase increases with increasing Cr content. This is mainly due to the increased volume fraction of the BCC / L21-Ni2AlTi phase, which promotes the growth of the L21-Ni2AlTi phase.

[0025] Cr has a higher melting point than Fe. As Cr continuously replaces Fe, it can be inferred that the liquidus temperature of the high-entropy alloy increases. This work uses the same flip-casting conditions, meaning it can be assumed that the temperature gradient within the liquid phase at the solid-liquid interface is the same. Considering the above factors, it can be concluded that, compared to the two alloys, the increased supercooling at the solidification front improves the nucleation rate, ultimately leading to grain refinement.

[0026] Finally, the relationship between microstructure and mechanical properties was established. Increasing the Cr / Fe ratio led to an increase in the BCC / L21-Ni2AlTi phase content and a decrease in the FCC phase content in the high-entropy alloy. Furthermore, the increased Cr / Fe ratio caused the FCC phase morphology to evolve from dendritic to equiaxed grain boundaries, and the alloy grains were refined. Increasing the Cr / Fe ratio significantly alters the tensile mechanical properties of the high-entropy alloys, specifically: yield strength: C13 alloy 608 MPa, C25 alloy 777 MPa, C36 alloy 1071 MPa, C47 alloy 1163 MPa, C67 alloy 1248 MPa; tensile strength: C13 alloy 958 MPa, C25 alloy 1142 MPa, C36 alloy 1260 MPa, C47 alloy 1342 MPa, C67 alloy 1295 MPa; total elongation at break: C13 alloy 20.6%, C25 alloy 9.5%, C36 alloy 3.1%, C47 alloy 2.2%, C67 alloy 1.1%. By increasing the Cr / Fe ratio, the tensile plasticity of the high-entropy alloys decreases, while the strength significantly increases, effectively enhancing the overall performance of the alloys, such as C13 and C25 alloys.

[0027] The advantages and beneficial effects of this invention are:

[0028] (1) This invention relates to a method for controlling the content of FCC phase and BCC / L21-Ni2AlTi phase in an alloy by changing the Cr / Fe ratio. Simultaneously, a large number of relatively uniformly distributed L21-Ni2AlTi nano-precipitates precipitate on the BCC matrix phase, achieving a nano-precipitation strengthening effect, thereby improving the microstructure and properties of Fe. 5-x Cr x NiAl 0.3 Ti 0.3 High-entropy alloys. These alloys are inexpensive to prepare and have simple and effective methods for controlling their properties. They are of great value for the development and application of high-entropy alloys in the Fe-Cr-Ni-Al-Ti system and related alloy systems reinforced by nano-precipitates.

[0029] (2) The Fe described in this invention 5-x Cr x NiAl 0.3 Ti 0.3 For alloys with (molar ratio) x = 1.13, 1.25, 1.36, 1.47 and 1.67, as the Cr / Fe ratio increases, the morphology of the FCC phase evolves from dendritic to equiaxed grain boundary shape, and the grains of the alloy are refined.

[0030] (3) The Fe described in this invention 5-x Cr x NiAl 0.3 Ti 0.3Alloys with (molar ratio) x = 1.13, 1.25, 1.36, 1.47 and 1.67 exhibit excellent comprehensive tensile mechanical properties by changing the Cr / Fe ratio.

[0031] In summary, research has revealed that the nano-precipitated phase-enhanced multiphase Fe of this invention... 5-x Cr x NiAl 0.3 Ti 0.3 The microstructure and properties of high-entropy alloys change with increasing Cr / Fe ratio, indicating that the microstructure and properties of this type of alloy can be effectively controlled by changing the Cr / Fe ratio. By adjusting the Cr / Fe ratio to control the content of the FCC phase and the BCC / L21-Ni2AlTi phase, a large number of relatively uniformly dispersed L21-Ni2AlTi nano-precipitates precipitate on the BCC matrix phase, resulting in nanoprecipitation strengthening. Furthermore, with increasing Cr content, the morphology of the FCC phase evolves from dendritic to equiaxed grain boundaries, and the alloy grains are refined. These two factors contribute to the ability to control the microstructure and properties of the alloy by increasing the Cr / Fe ratio. Attached Figure Description

[0032] Figure 1 As-cast Fe 5-x Cr x NiAl 0.3 Ti 0.3 X-ray diffraction pattern of the alloy plate.

[0033] Figure 2 As-cast Fe 5-x Cr x NiAl 0.3 Ti 0.3 Scanning electron micrographs of the alloy microstructure. (a)-(c) represent Fe. 3.87 Cr 1.13 NiAl 0.3 Ti 0.3 (d)-(f) represents Fe 3.75 Cr 1.25 NiAl 0.3 Ti 0.3 (g)-(i) represents Fe 3.64 Cr 1.36 NiAl 0.3 Ti 0.3 (j)-(l) represents Fe 3.53 Cr 1.47 NiAl 0.3 Ti 0.3 (m)-(o) represents Fe 3.33 Cr 1.67 NiAl0.3 Ti 0.3 .

[0034] Figure 3 As-cast Fe 5-x Cr x NiAl 0.3 Ti 0.3 Volume fraction statistics of FCC phase and BCC / L21-Ni2AlTi phase in high-entropy alloys.

[0035] Figure 4 As-cast Fe 3.87 Cr 1.13 NiAl 0.3 Ti 0.3 Transmission electron micrographs of the alloy microstructure. Among them, (a) shows the morphology of the precipitated phases and the selected area electron diffraction pattern of the alloy; (b)-(f) are TEM surface scan elemental distribution maps of the alloy; (g) is a high-magnification transmission electron micrograph of the alloy; (h) is a TEM line scan elemental distribution map of the indicated position (the arrow passing through the L21 nanoparticle in (g)).

[0036] Figure 5 As-cast Fe 5-x Cr x NiAl 0.3 Ti 0.3 Stress-strain curves of the alloy under tensile conditions. Detailed Implementation

[0037] In the specific implementation process, the nano-precipitated phase is enhanced by changing the Cr / Fe ratio. 5- x Cr x NiAl 0.3 Ti 0.3 The method for high-entropy alloys is as follows:

[0038] The composition range of Fe-Cr-Ni-Al-Ti high-entropy alloys can be varied according to the following principles: The Cr / Fe ratio can be modified to control the nano-precipitate strengthening effect. 5-x Cr x NiAl 0.3 Ti 0.3 (Molar ratio), x = 1.13, 1.25, 1.36, 1.47 and 1.67, and represented as C13, C25, C36, C47 and C67 respectively.

[0039] The raw material used is industrial-grade sponge Ti, with the purity of other elements not less than 99.9 wt.%. Alloy ingots were prepared by arc melting in a high-purity argon atmosphere (99.999% volume purity, 0.01–0.1 MPa). The ingots were repeatedly melted at least four times to ensure the homogeneity of the components. The alloy ingots were then remelted in an electric arc furnace under high-purity argon conditions, and a 10 mm × 5 mm alloy plate was obtained by copper mold flipping casting. Dog-bone shaped room-temperature tensile samples measuring 14 × 2 × 0.8 mm were cut from the alloy plate.

[0040] Nano-precipitated phases enhance multiphase Fe 5-x Cr x NiAl 0.3 Ti 0.3 The high-entropy alloy, by changing the Cr / Fe ratio to regulate the microstructure of the high-entropy alloy, includes: (1) changing the Cr / Fe ratio to change the content of the FCC phase and the BCC / L21-Ni2AlTi phase in the high-entropy alloy; (2) changing the Cr / Fe ratio to change the morphology of each phase, and at the same time, the grain size of the alloy also changes. Through microstructure detection, it was found that with the increase of the Cr / Fe ratio (i.e., Cr replacing Fe), the volume fraction of the BCC / L21-Ni2AlTi phase increases, the content of the FCC phase decreases, and at the same time, a large number of relatively uniformly distributed L21-Ni2AlTi nano-precipitates are obtained in the BCC / L21 region. The morphology of the FCC phase changes from dendritic to equiaxed grain boundary shape, and the grain size of the alloy is refined, such as Figure 2 As shown. The volume fractions of FCC phase and BCC / L21-Ni2AlTi phase in the high-entropy alloy are statistically represented as follows. Figure 3 As shown.

[0041] Through mechanical property testing, the present invention demonstrates nano-precipitated phase-reinforced multiphase Fe... 5-x Cr x NiAl 0.3 Ti 0.3 The performance indicators of high-entropy alloys are as follows:

[0042] Yield strength: C13 alloy 608MPa, C25 alloy 777MPa, C36 alloy 1071MPa, C47 alloy 1163MPa, C67 alloy 1248MPa; Tensile strength: C13 alloy 958MPa, C25 alloy 1142MPa, C36 alloy 1260MPa, C47 alloy 1342MPa, C67 alloy 1295MPa; Total elongation at break: C13 alloy 20.6%, C25 alloy 9.5%, C36 alloy 3.1%, C47 alloy 2.2%, C67 alloy 1.1%.

[0043] The present invention will now be described in detail through examples.

[0044] Example 1

[0045] This embodiment Fe 3.87 Cr 1.13 NiAl 0.3 Ti 0.3 (Molar ratio), i.e., C13 alloy, uses industrial-grade pure sponge Ti as raw material, with the purity of other elements not less than 99.9 wt.%. The raw materials are arranged in order of decreasing melting point from top to bottom, and the furnace pressure is reduced to 1.0 × 10⁻⁶ using mechanical and molecular pumps. -3 Pa ~ 3.0 × 10 -3 The pressure was increased to approximately 0.05 MPa by introducing high-purity Ar gas. Under argon protection, a master alloy ingot was prepared by arc melting, and the ingot was repeatedly melted five times. The ingot was then cast in a rotary furnace to obtain an alloy plate with dimensions of 10 mm wide, 5 mm thick, and 80 mm long. The alloy plate was cut using wire EDM and a high-speed saw to obtain tensile test specimens measuring 14 × 2 × 0.8 mm. The tensile test specimens were then sanded and polished.

[0046] The C13 as-cast alloy plate was sliced ​​to a thickness of approximately 1 mm, and the as-cast microstructure was characterized. For example... Figure 1 The X-ray diffraction pattern of the C13 alloy is shown. The C13 alloy is mainly composed of a disordered FCC phase, a disordered BCC matrix phase, and an ordered L21-Ni2AlTi nanoprecipitate phase. Based on the diffraction peaks of each phase of the alloy, the lattice constant α of the FCC phase can be calculated. FCC The lattice constant α of the BCC matrix phase BCC Lattice constant of L21-Ni2AlTi nanoprecipitates Then, according to the formula for calculating lattice mismatch ε Calculate the lattice mismatch between the BCC matrix phase and the L21-Ni2AlTi nanoprecipitates in this series of alloys. Therefore, the α of C13... FCC a BCC , ε were 0.3617 nm, 0.2880 nm, 0.5867 nm, and 1.84%, respectively. For example... Figure 2 As shown, from Figure 2 As can be seen from the microstructure of the high-entropy alloy. Figure 2As shown in (ac), the C13 alloy contains a dendritic FCC phase, a BCC matrix phase, and L21-Ni2AlTi phase nanoparticles precipitated on top of it, consistent with the X-ray diffraction analysis results. It is worth noting that the L21-Ni2AlTi nanoparticles at the boundary have a larger particle size compared to the center of the BCC / L21-Ni2AlTi phase region. The volume fraction of the C13 alloy was calculated: the FCC phase volume fraction was 35.7%, and the total volume fraction of the BCC matrix phase and L21-Ni2AlTi phase was 64.3%. (See [reference]). Figure 3 .

[0047] Figure 4 (a) shows the morphology of the precipitated phases and the selected area electron diffraction pattern of the C13 alloy. According to the TEM dark field phase and its diffraction pattern, the precipitated particles of the C13 alloy are L21-Ni2AlTi nano-precipitates, and the particle shape is approximately spherical. Figure 4 (b) to (f) are TEM scan elemental distribution diagrams of C13 alloy. It can be seen that granular L21 and blocky L21 are mainly rich in Al, Ni and Ti elements, while poor in Fe and Cr elements. In contrast, the BCC matrix phase is mainly rich in Fe and Cr elements, while poor in Al, Ni and Ti elements. Figure 4 (g) is a high-magnification transmission electron micrograph of the C13 alloy, showing a high density of mismatched dislocations at the phase boundary between the L21 nanoparticles and the BCC matrix. Figure 4 (g) is indicated by the arrow. Figure 4 (h) is the position shown. Figure 4 (g) TEM line scan elemental distribution map of the arrow passing through L21 nanoparticles. Comparing BCC and L21-Ni2AlTi phases, Cr and Fe elements are enriched in the BCC matrix phase, while Al, Ni and Ti elements are enriched in the L21 nanoprecipitate.

[0048] Tensile samples were cut from a C13 alloy plate (width, thickness, and length 10 mm, 5 mm, and 80 mm respectively), with dimensions of 14 × 2 × 0.8 mm and a tensile strain rate of 2 × 10⁻⁶. -4 s -1 . Figure 5 The tensile stress-strain curve of the high-entropy alloy is shown. The C13 alloy has a yield strength of 608 MPa, a tensile strength of 958 MPa, and a total elongation at break as high as 20.6%.

[0049] Example 2

[0050] This embodiment Fe 3.75 Cr 1.25 NiAl 0.3 Ti 0.3(Molar ratio), i.e., C25 alloy, uses industrial-grade pure sponge Ti as raw material, with the purity of other elements not less than 99.9 wt.%. The raw materials are arranged in order of decreasing melting point from top to bottom, and the furnace pressure is reduced to 1.0 × 10⁻⁶ using mechanical and molecular pumps. -3 Pa ~ 3.0 × 10 -3 The pressure was increased to approximately 0.05 MPa by introducing high-purity Ar gas. Under argon protection, a master alloy ingot was prepared by arc melting, and the ingot was repeatedly melted five times. The ingot was then cast in a rotary furnace to obtain an alloy plate with dimensions of 10 mm wide, 5 mm thick, and 80 mm long. The alloy plate was cut using wire EDM and a high-speed saw to obtain tensile test specimens measuring 14 × 2 × 0.8 mm. The tensile test specimens were then sanded and polished.

[0051] The C25 as-cast alloy plate was sliced ​​to a thickness of approximately 1 mm, and the as-cast microstructure was characterized. For example... Figure 1 The X-ray diffraction pattern of the C25 alloy is shown. The C25 alloy mainly consists of a disordered FCC phase, a disordered BCC matrix phase, and an ordered L21-Ni2AlTi nanoprecipitate phase. Based on the diffraction peaks of each phase, the lattice constant α of the FCC phase can be calculated. FCC The lattice constant α of the BCC matrix phase BCC Lattice constant of L21-Ni2AlTi nanoprecipitates Then, according to the formula for calculating lattice mismatch ε Calculate the lattice mismatch between the BCC matrix phase and the L21-Ni2AlTi nanoprecipitates in this series of alloys. Therefore, the a of C25 FCC a BCC , ε were 0.3617 nm, 0.2880 nm, 0.5870 nm, and 1.89%, respectively. For example... Figure 2 As shown, from Figure 2 As can be seen from the microstructure of the high-entropy alloy. Figure 2 As shown in (df), the C25 alloy contains a dendritic FCC phase, a BCC matrix phase, and L21-Ni2AlTi phase nanoparticles precipitated on it, which is consistent with the X-ray diffraction analysis results. It is worth noting that the L21-Ni2AlTi phase nanoparticles at the boundary have a larger particle size compared to the center of the BCC / L21-Ni2AlTi phase region. The volume fraction of the C25 alloy was calculated, with the FCC phase accounting for 23.6%, and the total integral of the BCC matrix phase and L21-Ni2AlTi phase accounting for 76.4%. (See...) Figure 3 .

[0052] Tensile samples were cut from a C25 alloy plate (width, thickness, and length 10 mm, 5 mm, and 80 mm respectively), with dimensions of 14 × 2 × 0.8 mm and a tensile strain rate of 2 × 10⁻⁶. -4 s -1 . Figure 5 The tensile stress-strain curve of the high-entropy alloy is shown. The C25 alloy has a yield strength of 777 MPa, a tensile strength of 1142 MPa, and a total elongation at break as high as 9.5%.

[0053] Example 3

[0054] This embodiment Fe 3.64 Cr 1.36 NiAl 0.3 Ti 0.3 (Molar ratio), i.e., C36 alloy, uses industrial-grade sponge Ti as raw material, with the purity of other elements not less than 99.9 wt.%. The raw materials are arranged in order of decreasing melting point from top to bottom, and the furnace pressure is reduced to 1.0 × 10⁻⁶ using mechanical and molecular pumps. -3 Pa ~ 3.0 × 10 -3 The pressure was increased to approximately 0.05 MPa by introducing high-purity Ar gas. Under argon protection, a master alloy ingot was prepared by arc melting, and the ingot was repeatedly melted five times. The ingot was then cast in a rotary furnace to obtain an alloy plate with dimensions of 10 mm wide, 5 mm thick, and 80 mm long. The alloy plate was cut using wire EDM and a high-speed saw to obtain tensile test specimens measuring 14 × 2 × 0.8 mm. The tensile test specimens were then sanded and polished.

[0055] The C36 as-cast alloy plate was sliced ​​to a thickness of approximately 1 mm, and the as-cast microstructure was characterized. For example... Figure 1 The X-ray diffraction pattern of the C36 alloy is shown. The C36 alloy mainly consists of a disordered FCC phase, a disordered BCC matrix phase, and an ordered L21-Ni2AlTi nanoprecipitate phase. Based on the diffraction peaks of each phase, the lattice constant α of the FCC phase can be calculated. FCC The lattice constant α of the BCC matrix phase BCC Lattice constant of L21-Ni2AlTi nanoprecipitates Then, according to the formula for calculating lattice mismatch ε Calculate the lattice mismatch between the BCC matrix phase and the L21-Ni2AlTi nanoprecipitates in this series of alloys. Therefore, the a of C36 FCC a BCC , ε were 0.3608 nm, 0.2870 nm, 0.5874 nm, and 2.31%, respectively. For example... Figure 2 As shown, from Figure 2 As can be seen from the microstructure of the high-entropy alloy. Figure 2 As shown in (gi), the C36 alloy contains FCC phases at grain boundaries and dendritic FCC phases, a BCC matrix phase, and L21-Ni2AlTi phase nanoparticles precipitated on top of it, which is consistent with the X-ray diffraction analysis results. It is worth noting that the L21-Ni2AlTi phase nanoparticles at the boundaries have a larger particle size compared to the center of the BCC / L21-Ni2AlTi phase region. The volume fraction of the C36 alloy was calculated, with the FCC phase accounting for 10.8%, and the total integral of the BCC matrix phase and L21-Ni2AlTi phase accounting for 89.2%. (See figure). Figure 3 .

[0056] Tensile samples were cut from a C36 alloy plate (width, thickness, and length 10 mm, 5 mm, and 80 mm respectively), with dimensions of 14 × 2 × 0.8 mm and a tensile strain rate of 2 × 10⁻⁶. -4 s -1 . Figure 5 The tensile stress-strain curve of the high-entropy alloy is shown. The C36 alloy has a yield strength of 1071 MPa, a tensile strength of 1260 MPa, and a total elongation at break as high as 3.1%.

[0057] Example 4

[0058] This embodiment Fe 3.53 Cr 1.47 NiAl 0.3 Ti 0.3 (Molar ratio), i.e., C47 alloy, uses industrial-grade sponge Ti as raw material, with the purity of other elements not less than 99.9 wt.%. The raw materials are arranged in order of decreasing melting point from top to bottom, and the furnace pressure is reduced to 1.0 × 10⁻⁶ using mechanical and molecular pumps. -3 Pa ~ 3.0 × 10 -3 The pressure was increased to approximately 0.05 MPa by introducing high-purity Ar gas. Under argon protection, a master alloy ingot was prepared by arc melting, and the ingot was repeatedly melted five times. The ingot was then cast in a rotary furnace to obtain an alloy plate with dimensions of 10 mm wide, 5 mm thick, and 80 mm long. The alloy plate was cut using wire EDM and a high-speed saw to obtain tensile test specimens measuring 14 × 2 × 0.8 mm. The tensile test specimens were then sanded and polished.

[0059] The C47 as-cast alloy plate was sliced ​​to a thickness of approximately 1 mm, and the as-cast microstructure was characterized. For example... Figure 1 The X-ray diffraction pattern of the C47 alloy is shown. The C47 alloy is mainly composed of a disordered FCC phase, a disordered BCC matrix phase, and an ordered L21-Ni2AlTi nanoprecipitate phase. Based on the diffraction peaks of each phase of the alloy, the lattice constant α of the FCC phase can be calculated. FCCThe lattice constant α of the BCC matrix phase BCC Lattice constant of L21-Ni2AlTi nanoprecipitates Then, according to the formula for calculating lattice mismatch ε Calculate the lattice mismatch between the BCC matrix phase and the L21-Ni2AlTi nanoprecipitates in this series of alloys. Therefore, the a of C47 FCC a BCC , ε were 0.3615 nm, 0.2878 nm, 0.5866 nm, and 1.89%, respectively. For example... Figure 2 As shown, from Figure 2 As can be seen from the microstructure of the high-entropy alloy. Figure 2 As shown in (jl), the C47 alloy contains an FCC phase at the grain boundaries, a BCC matrix phase, and L21-Ni2AlTi phase nanoparticles precipitated on top of it, which is consistent with the X-ray diffraction analysis results. It is worth noting that the L21-Ni2AlTi phase nanoparticles at the boundaries have a larger particle size compared to the center of the BCC / L21-Ni2AlTi phase region. The volume fraction of the C47 alloy was calculated, with the FCC phase accounting for 3.2%, and the total integral of the BCC matrix phase and L21-Ni2AlTi phase being 96.8%. (See [reference]). Figure 3 .

[0060] Tensile samples were cut from a C47 alloy plate (width, thickness, and length 10 mm, 5 mm, and 80 mm respectively), with dimensions of 14 × 2 × 0.8 mm and a tensile strain rate of 2 × 10⁻⁶. -4 s -1 . Figure 5 The tensile stress-strain curve of the high-entropy alloy is shown. The C36 alloy has a yield strength of 1163 MPa, a tensile strength of 1342 MPa, and a total elongation at break as high as 2.2%.

[0061] Example 5

[0062] This embodiment Fe 3.33 Cr 1.67 NiAl 0.3 Ti 0.3 (Molar ratio), i.e., C67 alloy, uses industrial-grade pure sponge Ti as raw material, with the purity of other elements not less than 99.9 wt.%. The raw materials are arranged in order of decreasing melting point from top to bottom, and the furnace pressure is reduced to 1.0 × 10⁻⁶ using mechanical and molecular pumps. -3 Pa ~ 3.0 × 10 -3The pressure was increased to approximately 0.05 MPa by introducing high-purity Ar gas. Under argon protection, a master alloy ingot was prepared by arc melting, and the ingot was repeatedly melted five times. The ingot was then cast in a rotary furnace to obtain an alloy plate with dimensions of 10 mm wide, 5 mm thick, and 80 mm long. The alloy plate was cut using wire EDM and a high-speed saw to obtain tensile test specimens measuring 14 × 2 × 0.8 mm. The tensile test specimens were then sanded and polished.

[0063] The C67 as-cast alloy plate was sliced ​​to a thickness of approximately 1 mm, and the as-cast microstructure was characterized. For example... Figure 1 The X-ray diffraction pattern of the C67 alloy is shown. The C67 alloy is mainly composed of a disordered BCC matrix phase and an ordered L21-Ni2AlTi nanoprecipitate phase. Based on the diffraction peaks of each phase of the alloy, the lattice constant α of the BCC matrix phase can be calculated. BCC Lattice constant of L21-Ni2AlTi nanoprecipitates Then, according to the formula for calculating lattice mismatch ε Calculate the lattice mismatch between the BCC matrix phase and the L21-Ni2AlTi nanoprecipitates in this series of alloys. Therefore, the a of C67 BCC , ε were 0.2879 nm, 0.5870 nm, and 1.93%, respectively. For example... Figure 2 As shown, from Figure 2 As can be seen from the microstructure of the high-entropy alloy. Figure 2 As shown in (mo), the C67 alloy contains a BCC matrix phase and L21-Ni2AlTi phase nanoparticles precipitated on it, consistent with the X-ray diffraction analysis results. It is worth noting that the L21-Ni2AlTi phase nanoparticles at the boundary have a larger particle size compared to the center of the BCC / L21-Ni2AlTi phase region. The C67 alloy does not contain an FCC phase, see [reference needed]. Figure 3 .

[0064] Tensile samples were cut from a C67 alloy plate (width, thickness, and length 10 mm, 5 mm, and 80 mm respectively), with dimensions of 14 × 2 × 0.8 mm and a tensile strain rate of 2 × 10⁻⁶. -4 s -1 . Figure 5 The tensile stress-strain curve of the high-entropy alloy is shown. The C36 alloy has a yield strength of 1248 MPa, a tensile strength of 1295 MPa, and a total elongation at break as high as 1.1%.

[0065] The results of the embodiments show that, by changing the Cr / Fe ratio, the present invention can not only maintain a large number of relatively uniformly distributed L21 nano-precipitates, but also control the relative content of FCC phase and BCC / L21 phase. Furthermore, as the Cr / Fe ratio increases, the morphology of the FCC phase evolves from dendritic to equiaxed grain boundary shape, and the alloy grains are refined. These two factors mean that changing the Cr / Fe ratio can control the microstructure of the high-entropy alloy, thereby affecting its mechanical properties. The present invention provides a method for strengthening multiphase Fe with nano-precipitates. 5-x Cr x NiAl 0.3 Ti 0.3 The practical application of high-entropy alloys, as well as the development of high-entropy alloys in other similar alloy systems, are of great value.

Claims

1. A nano-precipitated phase-enhanced multiphase Fe 5-x Cr x NiAl 0.3 Ti 0.3 High-entropy alloy, characterized in that, The high-entropy alloy, by molar ratio, has an alloy composition following Fe 5-x Cr x NiAl 0.3 Ti 0.3 , x =1.13, 1.25, 1.36, 1.47 and 1.67, and represented as C13, C25, C36, C47 and C67 respectively; The high-entropy alloy has three phases: a disordered FCC phase, a disordered BCC matrix phase, and a nano-scale ordered L21-Ni2AlTi phase precipitated on the BCC matrix phase. The L21-Ni2AlTi nano-precipitates have nucleation capabilities. The high-entropy alloy is obtained by casting with a copper mold, and a large number of dispersed spherical L21-Ni2AlTi nano-precipitates are precipitated in the alloy. As the Cr content of the high-entropy alloy increases, i.e. Cr replacing Fe increases the Cr / Fe ratio, the volume fraction of the BCC / L21-Ni2AlTi phase increases accordingly, the volume fraction of the FCC phase decreases accordingly, the morphology of the FCC phase evolves from dendritic to equiaxed grain boundary shape, and the grains of the alloy are refined. By adding Cr, the tensile mechanical properties of the high-entropy alloys changed significantly; specifically, the yield strength was: C13 alloy 608 MPa, C25 alloy 777 MPa, C36 alloy 1071 MPa, C47 alloy 1163 MPa, and C67 alloy 1248 MPa; the tensile strength was: C13 alloy 958 MPa, C25 alloy 1142 MPa, C36 alloy 1260 MPa, C47 alloy 1342 MPa, and C67 alloy 1295 MPa; and the total elongation at break was: C13 alloy 20.6%, C25 alloy 9.5%, C36 alloy 3.1%, C47 alloy 2.2%, and C67 alloy 1.1%.

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