Strong-toughness metastable medium-entropy alloy and preparation method thereof

Abstract

The invention provides a high-toughness metastable medium-entropy alloy and a preparation method thereof, and belongs to the technical field of metastable medium-entropy alloy preparation. According to the preparation method of the high-toughness metastable medium-entropy alloy, by adding interstitial atoms into the metastable medium-entropy alloy, the free energy difference of FCC and BCC phases is changed, so that the martensite transformation rate is changed, the stable high strain hardening rate of the material is maintained in the deformation process, and the toughness of the material is improved; through additive manufacturing forming, due to the unique machining sequence of additive manufacturing, workpieces with extremely complex three-dimensional shapes can be machined, meanwhile, a unique cellular structure can be formed, and therefore the yield strength of the alloy material is further improved. The result of the embodiment shows that the yield strength of the prepared high-toughness metastable medium-entropy alloy is 847.5 MPa, the tensile strength of the prepared high-toughness metastable medium-entropy alloy is 1398.2 MPa, and the elongation at break of the prepared high-toughness metastable medium-entropy alloy is 52.2%.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of metastable medium entropy alloys, and in particular to a strong and tough metastable medium entropy alloy and a preparation method thereof. Background Art

[0002] Medium-entropy alloys (MEAs) are a new class of high-performance metallic materials that have emerged in recent years and hold great potential for application. Their exceptional damage tolerance at low temperatures has garnered considerable attention as the next generation of low-temperature alloys. Metastable MEAs, a key branch of the MEA family, exhibit excellent mechanical properties at both low and room temperatures, promising broad applications in aerospace, nuclear energy, and automotive applications. Compared to conventional engineering defect strengthening techniques—such as interface strengthening, dislocation strengthening, and precipitation strengthening—MEAs rely primarily on martensitic transformation-induced plasticity to achieve synergistic optimization of strength and ductility. By inducing a phase transformation (austenite-martensite) under specific temperature and strain conditions, MEAs can absorb significant deformation energy while maintaining high strength, resulting in excellent low-temperature mechanical properties. However, the influence of the martensitic transformation on the overall deformation behavior of the material is complex. When the transformation rate is too fast, significant work-hardening is observed initially, but the work-hardening rate rapidly decreases after reaching its peak, accompanied by a rapid reduction in the tough austenite phase. This in turn limits the material's elongation and overall plastic deformation capacity. This phenomenon not only restricts the application of materials under large deformation conditions, but also puts higher demands on how to precisely control phase change behavior.

[0003] By adding interstitial atoms to metastable medium-entropy alloys, the martensitic transformation rate can be effectively controlled to achieve an excellent strength-elongation combination. In traditional manufacturing, the method of adding interstitial atoms to metastable medium-entropy alloys usually relies on adding gases during the melting stage (such as nitriding or carburizing treatments), allowing the interstitial atoms to diffuse into the crystal lattice at high temperatures. Although this method can improve the strength and elongation of the alloy, it is easily limited by solubility, phase precipitation, and grain coarsening. As a result, the interstitial atoms have a poor effect on improving the alloy's properties, making it difficult to meet the specific material performance requirements of low-temperature engineering applications.

[0004] Therefore, how to improve the regulation effect of interstitial atoms on the properties of metastable medium-entropy alloys, so as to obtain metastable medium-entropy alloys with excellent strength-elongation, has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a strong and tough metastable medium entropy alloy and a preparation method thereof. The strong and tough metastable medium entropy alloy obtained by the preparation method provided by the present invention has significantly improved yield strength, tensile strength and elongation at break compared to pure metastable medium entropy alloy.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a strong and tough metastable medium entropy alloy, comprising the following steps:

[0008] (1) mixing metal element raw materials of a metastable medium entropy alloy, pre-alloying them, and atomizing and drying them in sequence to obtain a metastable medium entropy alloy powder, and then mixing the metastable medium entropy alloy powder with particles containing interstitial atoms to obtain a mixed powder;

[0009] Alternatively, the metal elemental raw material of the metastable medium entropy alloy and the particles containing interstitial atoms are mixed and then ball-milled or pre-alloyed to obtain a mixed powder;

[0010] (2) The mixed powder obtained in step (1) is subjected to additive manufacturing to obtain a strong and tough metastable medium entropy alloy.

[0011] Preferably, the chemical composition of the metastable medium entropy alloy in step (1) is Fe a (CoNi) 90-a Cr 10 , where a is 50 to 65.

[0012] Preferably, the metal element raw materials of the metastable medium entropy alloy in step (1) include metal cobalt, metal chromium, metal nickel and metal iron; the purity of the metal element raw materials is independently greater than 99.9%.

[0013] Preferably, the particle size of the metastable medium entropy alloy powder in step (1) is 15 to 53 μm.

[0014] Preferably, the interstitial atom-containing particles in step (1) include any one of TiC nanoparticles, graphite particles and Cr2O3 particles; and the particle size of the TiC nanoparticles is 100 to 300 nm.

[0015] Preferably, the mass of the particles containing interstitial atoms in step (1) is 0.5 to 3% of the mass of the metastable medium entropy alloy.

[0016] Preferably, in step (1), the metastable medium entropy alloy powder and the particles containing interstitial atoms are mixed by ball milling, the ball-to-material ratio of the ball milling is (1-5):1, the ball milling speed is 100-500 rpm, and the ball milling time is 5-10 h.

[0017] Preferably, the particle size of the mixed powder in step (1) is 15 to 53 μm.

[0018] Preferably, the process parameters of the additive manufacturing molding in step (2) include: powder laying amount of 100-150 μm, powder layer thickness of the molding platform of 20-50 μm, laser power of 125-200 W, spot radius of 20-50 μm, overlap spacing of 40-70 μm, and scanning speed of 500-1500 mm / s.

[0019] The present invention provides a strong and tough metastable medium entropy alloy prepared by the preparation method described in the above technical solution, wherein the strong and tough metastable medium entropy alloy comprises a metastable medium entropy alloy and interstitial atoms, and the interstitial atoms comprise at least one of carbon, nitrogen and oxygen.

[0020] The present invention provides a method for preparing a strong and tough metastable medium entropy alloy, comprising the following steps: (1) mixing the metal elemental raw materials of the metastable medium entropy alloy, and then pre-alloying and atomizing and drying in sequence to obtain a metastable medium entropy alloy powder, and then mixing the metastable medium entropy alloy powder with particles containing interstitial atoms to obtain a mixed powder; or, mixing the metal elemental raw materials of the metastable medium entropy alloy with particles containing interstitial atoms, and then ball milling or pre-alloying to obtain a mixed powder; (2) subjecting the mixed powder obtained in step (1) to additive manufacturing to obtain a strong and tough metastable medium entropy alloy. The present invention uses particles containing interstitial atoms to add interstitial atoms to the metastable medium entropy alloy, thereby changing the free energy difference between the FCC and BCC phases, thereby changing the rate of martensitic transformation, allowing the material to maintain a stable high strain hardening rate during deformation, and improving the toughness of the material; through additive manufacturing, due to the unique processing sequence of additive manufacturing, workpieces with extremely complex three-dimensional shapes can be processed, and a unique cellular structure can be formed, thereby further improving the yield strength of the alloy material. The preparation method provided by the present invention is simple and easy to operate, and has good universality and application prospects. The results of the embodiments show that in the strong and tough metastable medium entropy alloy provided by the present invention, a cellular structure composed of dislocation walls exists inside the large grains, and interstitial compounds can be observed to be mainly distributed near the boundaries of the cellular structure; at the same time, the strong and tough metastable medium entropy alloy prepared by the present invention has a yield strength increased from 491.8 MPa to 847.5 MPa, a tensile strength increased from 1264.3 MPa to 1398.2 MPa, and an elongation at break increased from 30.1% to 52.2% relative to the pure metastable medium entropy alloy, indicating that the preparation method provided by the present invention significantly improves the strength and toughness of the metastable medium entropy alloy by introducing interstitial atoms. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of the strong and tough metastable medium entropy alloy prepared in Example 1 of the present invention;

[0022] Figure 2 This is a comparison chart of the mechanical properties of the strong and tough metastable medium entropy alloy prepared in Example 1 and the metastable medium entropy alloy prepared in Comparative Example 1. DETAILED DESCRIPTION

[0023] The present invention provides a method for preparing a strong and tough metastable medium entropy alloy, comprising the following steps:

[0024] (1) mixing metal element raw materials of a metastable medium entropy alloy, pre-alloying them, and atomizing and drying them in sequence to obtain a metastable medium entropy alloy powder, and then mixing the metastable medium entropy alloy powder with particles containing interstitial atoms to obtain a mixed powder;

[0025] Alternatively, the metal elemental raw material of the metastable medium entropy alloy and the particles containing interstitial atoms are mixed and then ball-milled or pre-alloyed to obtain a mixed powder;

[0026] (2) The mixed powder obtained in step (1) is subjected to additive manufacturing to obtain a strong and tough metastable medium entropy alloy.

[0027] In the present invention, unless otherwise specified, the raw materials used in the present invention are commercially available products well known to those skilled in the art or products obtained by known methods.

[0028] The invention mixes metal element raw materials of a metastable medium entropy alloy, performs pre-alloying and atomization drying in sequence to obtain metastable medium entropy alloy powder, and then mixes the metastable medium entropy alloy powder with particles containing interstitial atoms to obtain mixed powder.

[0029] In the present invention, the chemical composition of the metastable medium entropy alloy is preferably Fe a (CoNi) 90-a Cr 10 In the present invention, a is preferably 50 to 65. As an embodiment of the present invention, a is 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63 or 64. The metastable medium entropy alloy provided by the present invention exhibits excellent mechanical properties at low temperatures and room temperatures.

[0030] In the present invention, the metal raw materials for the metastable medium entropy alloy preferably include cobalt, chromium, nickel, and iron; the purity of each of the metal raw materials is preferably greater than 99.9%. The present invention does not particularly limit the specific amount of the metal raw materials used in the metastable medium entropy alloy, as long as the chemical composition of the metastable medium entropy alloy meets the requirements.

[0031] The present invention has no special restrictions on the specific operations and process parameters of the pre-alloying and atomization drying. They can be determined according to the technical common sense of those skilled in the art so as to enable the components to be evenly mixed and form a metastable medium entropy alloy powder with a particle size that meets the requirements.

[0032] In the present invention, the particle size of the metastable medium entropy alloy powder is preferably 15 to 53 μm. As an embodiment of the present invention, the particle size of the metastable medium entropy alloy powder can be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm. The present invention controls the particle size of the metastable medium entropy alloy powder to facilitate subsequent additive manufacturing and prepare a highly dense metastable medium entropy alloy, thereby further improving its strength and toughness.

[0033] In the present invention, when the particle size of the metastable medium entropy alloy powder does not meet the above requirements, the present invention preferably further comprises screening the metastable medium entropy alloy powder. The present invention has no particular limitation on the specific operation of the screening, as long as the particle size of the metastable medium entropy alloy powder meets the requirements.

[0034] In the present invention, the interstitial atom-containing particles preferably include any one of TiC nanoparticles, graphite particles, and Cr2O3 particles, more preferably TiC nanoparticles. The mass of the interstitial atom-containing particles is preferably 0.5-3% of the mass of the metastable medium entropy alloy. In the present invention, the particle size of the TiC nanoparticles is preferably 100-300 nm. As one embodiment of the present invention, the mass of the interstitial atom-containing particles can be 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, or 2.5% of the mass of the metastable medium entropy alloy powder. The particle size of the TiC nanoparticles can be 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, or 280 nm. The present invention introduces interstitial atoms by adding particles containing interstitial atoms into a metastable medium entropy alloy, changes the free energy difference between the FCC and BCC phases, and thus changes the rate of martensitic transformation, enabling the material to maintain a stable high strain hardening rate during deformation and improving the toughness of the material. By controlling the type and amount of interstitial atoms, the toughness of the metastable medium entropy alloy is further improved.

[0035] In the present invention, the method of mixing the metastable medium entropy alloy powder and the particles containing interstitial atoms is preferably ball milling; the ball-to-material ratio of the ball milling mixing is preferably (1-5):1; the rotation speed of the ball milling mixing is preferably 100-500 rpm; and the time of the ball milling mixing is preferably 5-10 hours. As an embodiment of the present invention, the ball-to-material ratio of the ball milling mixing can be (2-4):1, or (2-3):1; the rotation speed of the ball milling mixing can be 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm or 450rpm; and the time of the ball milling mixing can be 6h, 7h, 8h or 9h. The present invention can uniformly mix the metastable medium entropy alloy powder and the particles containing interstitial atoms by adopting the method of ball milling mixing.

[0036] After obtaining the mixed powder, the present invention preferably further comprises vacuum drying the mixed powder. The present invention has no special limitation on the specific operation of the vacuum drying, as long as the mixed powder can be dried without introducing impurities. As an embodiment of the present invention, the temperature of the vacuum drying can be 50 to 100°C, or 60°C, 70°C, 80°C or 90°C; the time of the vacuum drying can be 1 to 5h, or 2h, 3h or 4h; the vacuum drying is preferably carried out in a vacuum chamber. The present invention has no special limitation on the vacuum degree of the vacuum drying, and it can be determined according to the technical common sense of those skilled in the art, as long as the introduction of impurities can be avoided.

[0037] The invention mixes a metal element raw material of a metastable medium entropy alloy with particles containing interstitial atoms and then performs ball milling or pre-alloying to obtain a mixed powder.

[0038] In the present invention, the chemical composition of the metastable medium entropy alloy is preferably the same as the chemical composition of the aforementioned metastable medium entropy alloy, which will not be described in detail here.

[0039] In the present invention, the purity and amount of the metal element raw material of the metastable medium entropy alloy are preferably the same as those described above, and will not be described in detail here.

[0040] In the present invention, the particles containing interstitial atoms preferably include TiC nanoparticles and / or graphite particles, more preferably graphite particles. In the present invention, the amount of the particles containing interstitial atoms is preferably the same as described above and will not be described in detail herein. The present invention has no particular limitation on the particle size of the particles containing interstitial atoms, and can be determined according to the technical common sense of those skilled in the art. The present invention introduces interstitial atoms by adding particles containing interstitial atoms to a metastable medium entropy alloy, changes the free energy difference between the FCC and BCC phases, thereby changing the rate of martensitic transformation, allowing the material to maintain a stable high strain hardening rate during deformation, and improving the toughness of the material; by controlling the type and amount of interstitial atoms, it is beneficial to further enhance the toughness of the metastable medium entropy alloy.

[0041] The present invention has no particular limitation on the specific operation of the ball milling. The ball milling operation familiar to those skilled in the art can be used to uniformly mix the metal elemental raw material of the metastable medium entropy alloy and the particles containing interstitial atoms and to ensure that the particle size of the mixed powder meets the requirements.

[0042] In the present invention, the pre-alloying is preferably performed in a vacuum induction melting furnace. The present invention has no particular limitation on the specific model and source of the vacuum induction melting furnace, and a commercially available vacuum induction melting furnace well known to those skilled in the art can be used.

[0043] In the present invention, the vacuum degree of the pre-alloying is preferably 1×10 -3 ~1×10-2 The present invention can remove most of the impurities such as oxygen by controlling the vacuum degree of pre-alloying, thereby reducing the content of impurities introduced during the smelting process.

[0044] The present invention has no particular limitation on the temperature and time of the pre-alloying, as long as the metal element raw material and the particles containing interstitial atoms are completely melted and mixed uniformly. The present invention can promote alloy homogenization through pre-alloying.

[0045] In the present invention, the particle size of the mixed powder is preferably 15 to 53 μm. As an embodiment of the present invention, the particle size of the mixed powder can be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm. By controlling the particle size of the mixed powder, the present invention facilitates subsequent additive manufacturing and produces a highly dense metastable medium entropy alloy, thereby further improving its strength and toughness.

[0046] In the present invention, when the particle size of the mixed powder does not meet the above requirements, the present invention preferably further comprises screening the mixed powder. The present invention has no particular limitation on the specific operation of the screening, as long as the particle size of the mixed powder meets the requirements.

[0047] After obtaining the mixed powder, the present invention preferably further comprises vacuum drying the mixed powder. The present invention has no special limitation on the specific operation of the vacuum drying, as long as the mixed powder can be dried without introducing impurities. As an embodiment of the present invention, the temperature of the vacuum drying can be 50 to 100°C, or 60°C, 70°C, 80°C or 90°C; the time of the vacuum drying can be 1 to 5h, or 2h, 3h or 4h; the vacuum drying is preferably carried out in a vacuum chamber. The present invention has no special limitation on the vacuum degree of the vacuum drying, and it can be determined according to the technical common sense of those skilled in the art, as long as the introduction of impurities can be avoided.

[0048] After obtaining the mixed powder, the present invention performs additive manufacturing on the mixed powder to obtain a strong and tough metastable medium entropy alloy.

[0049] In the present invention, the process parameters of the additive manufacturing molding preferably include: a powder spreading amount of 100-150 μm, a powder layer thickness of a molding platform of 20-50 μm, a laser power of 125-200 W, a spot radius of 20-50 μm, an overlap spacing of 40-70 μm, and a scanning speed of 500-1500 mm / s. As an embodiment of the present invention, the powder spreading amount can be 110 μm, 120 μm, 130 μm or 140 μm; the powder layer thickness of the molding platform can be 25 μm, 30 μm, 35 μm, 40 μm or 45 μm; the laser power can be 130 W, 135 W, 140 W, 145 W, 150 W, 155 W, 160 W, 165 W, 170 W, 175 W, 180 W, 185 W, 190 W or 1 95W; the spot radius can be 25μm, 30μm, 35μm, 40μm or 45μm; the overlap spacing can be 45μm, 50μm, 55μm, 60μm or 65μm; the scanning speed can be 600mm / s, 700mm / s, 800mm / s, 900mm / s, 1000mm / s, 1100mm / s, 1200mm / s, 1300mm / s or 1400mm / s. The present invention is formed by additive manufacturing. Due to the unique processing sequence of additive manufacturing, it can process workpieces with extremely complex three-dimensional shapes; at the same time, the process parameters of additive manufacturing are controlled. Due to the fast scanning speed and small molten pool size, the cooling rate is faster than traditional manufacturing. In this process, a unique cellular structure can be formed, thereby further improving the yield strength of the alloy material.

[0050] The preparation method provided by the present invention is simple, easy to operate, and has good universality and application prospects.

[0051] The present invention also provides a strong and tough metastable medium entropy alloy prepared by the preparation method described in the above technical solution.

[0052] In the present invention, the strong and tough metastable medium entropy alloy comprises a metastable medium entropy alloy and interstitial atoms, and the interstitial atoms comprise at least one of carbon, nitrogen and oxygen.

[0053] In the present invention, the chemical composition of the metastable medium entropy alloy is preferably Fe a (CoNi) 90-a Cr 10 In the present invention, a is preferably 50 to 65. As an embodiment of the present invention, a is 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63 or 64. The metastable medium entropy alloy provided by the present invention exhibits excellent mechanical properties at low temperatures and room temperatures.

[0054] In the present invention, the mass percentage of interstitial atoms in the strong and tough metastable medium entropy alloy is preferably ≤3%. As one embodiment of the present invention, the mass percentage of interstitial atoms in the strong and tough metastable medium entropy alloy can be 0.1%, 0.5%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, or 2.5%. By adding interstitial atoms to the metastable medium entropy alloy, the present invention changes the free energy difference between the FCC and BCC phases, thereby changing the rate of martensitic transformation, allowing the material to maintain a stable high strain hardening rate during deformation, and improving the toughness of the material; by controlling the type and amount of interstitial atoms, it is beneficial to further enhance the toughness of the metastable medium entropy alloy.

[0055] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] Example 1

[0057] A method for preparing a strong and tough metastable medium entropy alloy comprises the following steps:

[0058] (1) The metal element raw materials of the metastable medium entropy alloy are mixed and then pre-alloyed and atomized and dried in sequence, and the metastable medium entropy alloy powder with a particle size of 15 to 53 μm is obtained after screening, and the metastable medium entropy alloy powder and particles containing interstitial atoms are then ball-milled and mixed, and finally vacuum dried in a vacuum chamber to obtain a mixed powder; the chemical composition of the metastable medium entropy alloy is Fe 65 (CoNi) 25 Cr 10 The metal elemental raw materials of the metastable medium entropy alloy are cobalt, chromium, nickel and iron with a purity of >99.9%; the particles containing interstitial atoms are TiC nanoparticles with a particle size of 100 to 300 nm, and the mass of the TiC nanoparticles is 3% of the mass of the metastable medium entropy alloy powder; the ball-to-material ratio of the ball milling mixing is 2:1, the rotation speed is 200 rpm, and the time is 8 hours; the temperature of the vacuum drying is 80°C and the time is 2 hours;

[0059] (2) The mixed powder obtained in step (1) is immediately fed into the SLM system to prevent contamination and moisture, and then additive manufacturing is performed according to the set scanning path to obtain a strong and tough metastable medium entropy alloy; the process parameters of the additive manufacturing are: the powder spreading amount is 100 μm, the powder layer thickness of the forming platform is 30 μm, the laser power is 175 W, the spot radius is 30 μm, the overlap spacing is 70 μm, and the scanning speed is 900 mm / s; after the single-layer scanning is completed, the laser beam is turned off, the laser head is rotated 67°, and the powder spreading-selective scanning melting process is repeated until the manufacture of the strong and tough metastable medium entropy alloy is completed.

[0060] The microstructure of the strong and tough metastable medium entropy alloy prepared in Example 1 was characterized by scanning electron microscopy (SEM). Figure 1 As shown. Figure 1 It can be seen that in the strong-tough metastable medium-entropy alloy, there is a cellular structure composed of dislocation walls inside the large grains, and it can be observed that the interstitial compounds are mainly distributed near the boundaries of the cellular structure.

[0061] Comparative Example 1

[0062] A method for preparing a metastable medium entropy alloy comprises the following steps:

[0063] (1) The metal element raw materials of the metastable medium entropy alloy are mixed and then pre-alloyed and atomized and dried in sequence, and then sieved and vacuum dried in a vacuum chamber to obtain a metastable medium entropy alloy powder with a particle size of 15 to 53 μm; the chemical composition of the metastable medium entropy alloy is Fe 65 (CoNi) 25 Cr 10 The metal element raw materials of the metastable medium entropy alloy are metal cobalt, metal chromium, metal nickel and metal iron with a purity of >99.9%; the vacuum drying temperature is 80°C and the time is 2h;

[0064] (2) The metastable medium entropy alloy powder obtained in step (1) is immediately fed into the SLM system to prevent contamination and moisture, and then additive manufacturing is performed according to the set scanning path to obtain the metastable medium entropy alloy; the process parameters of the additive manufacturing are: the powder spreading amount is 100 μm, the powder layer thickness of the forming platform is 30 μm, the laser power is 175 W, the spot radius is 30 μm, the overlap spacing is 70 μm, and the scanning speed is 900 mm / s; after the single-layer scanning is completed, the laser beam is turned off, the laser head is rotated 67°, and the powder spreading-selective area scanning melting process is repeated.

[0065] The high-toughness metastable medium entropy alloy prepared in Example 1 and the metastable medium entropy alloy prepared in Comparative Example 1 were subjected to 93K low-temperature uniaxial static tensile tests. The results are as follows: Figure 2 As shown. Figure 2It can be seen that the yield strength of the metastable medium entropy alloy prepared in Comparative Example 1 is 491.8 MPa, the tensile strength is 1264.3 MPa, and the elongation at break is 30.1%. Relative to Comparative Example 1, the yield strength of the strong and tough metastable medium entropy alloy prepared by the present invention is increased from 491.8 MPa to 847.5 MPa, and the tensile strength is increased from 1264.3 MPa to 1398.2 MPa. At the same time, the elongation at break is increased from 30.1% to 52.2%, indicating that the preparation method provided by the present invention significantly improves the strength and toughness of the metastable medium entropy alloy by introducing interstitial atoms.

[0066] Example 2

[0067] A method for preparing a strong and tough metastable medium entropy alloy comprises the following steps:

[0068] (1) Place the metal element raw materials of the metastable medium entropy alloy and graphite particles into a vacuum induction melting furnace and control the vacuum degree to ≤1×10 -2 Pa, then open the induction coil to melt until completely melted and keep warm for 30 minutes for pre-alloying, then perform atomization drying, and finally vacuum dry at 80 ° C for 2 hours to obtain a mixed powder with a particle size of 15 to 53 μm; the chemical composition of the metastable medium entropy alloy is Fe 60 (CoNi) 30 Cr 10 The metal element raw materials of the metastable medium entropy alloy are metal cobalt, metal chromium, metal nickel and metal iron with a purity of >99.9%; the mass of the graphite particles is 2% of the mass of the metastable medium entropy alloy;

[0069] (2) The mixed powder obtained in step (1) is immediately fed into the SLM system to prevent contamination and moisture, and then additive manufacturing is performed according to the set scanning path to obtain a strong and tough metastable medium entropy alloy; the process parameters of the additive manufacturing are: the powder spreading amount is 120 μm, the powder layer thickness of the forming platform is 30 μm, the laser power is 150 W, the spot radius is 30 μm, the overlap spacing is 60 μm, and the scanning speed is 900 mm / s; after the single-layer scanning is completed, the laser beam is turned off, the laser head is rotated 67°, and the powder spreading-selective scanning melting process is repeated until the manufacture of the strong and tough metastable medium entropy alloy is completed.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a strong and tough metastable medium entropy alloy, characterized in that: The following steps are involved: (1) mixing metal element raw materials of a metastable medium entropy alloy, pre-alloying them, and atomizing and drying them in sequence to obtain a metastable medium entropy alloy powder, and then mixing the metastable medium entropy alloy powder with particles containing interstitial atoms to obtain a mixed powder; Alternatively, the metal elemental raw material of the metastable medium entropy alloy and the particles containing interstitial atoms are mixed and then ball-milled or pre-alloyed to obtain a mixed powder; (2) The mixed powder obtained in step (1) is subjected to additive manufacturing to obtain a strong and tough metastable medium entropy alloy.

2. The preparation method according to claim 1, characterized in that The chemical composition of the metastable medium entropy alloy in step (1) is Fe a (CoNi) 90-a Cr 10 , where a is 50 to 65.

3. The preparation method according to claim 1, characterized in that The metal element raw materials of the metastable medium entropy alloy in step (1) include metal cobalt, metal chromium, metal nickel and metal iron; the purity of the metal element raw materials is independently greater than 99.9%.

4. The preparation method according to claim 1, characterized in that The particle size of the metastable medium entropy alloy powder in step (1) is 15 to 53 μm.

5. The preparation method according to claim 1, characterized in that The particles containing interstitial atoms in step (1) include any one of TiC nanoparticles, graphite particles and Cr2O3 particles; the particle size of the TiC nanoparticles is 100 to 300 nm.

6. The preparation method according to claim 1, characterized in that The mass of the particles containing interstitial atoms in step (1) is 0.5-3% of the mass of the metastable medium entropy alloy.

7. The preparation method according to claim 1, characterized in that In the step (1), the metastable medium entropy alloy powder and the particles containing interstitial atoms are mixed by ball milling, the ball-to-material ratio of the ball milling is (1-5):1, the rotation speed of the ball milling is 100-500 rpm, and the ball milling time is 5-10 hours.

8. The preparation method according to claim 1, characterized in that The particle size of the mixed powder in step (1) is 15 to 53 μm.

9. The preparation method according to claim 1, characterized in that The process parameters of the additive manufacturing molding in step (2) include: powder spreading amount of 100-150 μm, powder layer thickness of the molding platform of 20-50 μm, laser power of 125-200 W, spot radius of 20-50 μm, overlap spacing of 40-70 μm, and scanning speed of 500-1500 mm / s.

10. The strong and tough metastable medium entropy alloy prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The strong and tough metastable medium entropy alloy comprises a metastable medium entropy alloy and interstitial atoms, wherein the interstitial atoms comprise at least one of carbon, nitrogen and oxygen.

Images