A dual-phase soft magnetic high-entropy alloy and a preparation method thereof

Abstract

The application discloses a kind of dual-phase soft magnetic high-entropy alloy and preparation method thereof.The high-entropy alloy is composed of iron (Fe), cobalt (Co), chromium (Cr) and vanadium (V), with face-centered cubic (FCC) and body-centered cubic (BCC) dual-phase structure.The preparation method includes the following steps: design of dual-phase high-entropy alloy; preparation of alloy; homogenization treatment; controlled cold rolling; two-stage isothermal treatment.Based on the above process, the prepared high-entropy alloy has FCC and BCC dual-phase, FCC phase rich in Co, Cr and V, and BCC rich in Fe.Two-phase layered lamellar phase alternately forms pearlite-like structure.The dual-phase soft magnetic high-entropy alloy has high saturation magnetization (50-200 emu / g), low coercivity (50-100 Oe), high tensile yield strength (800-2000 MPa) and moderate plasticity (10-30%), and the mechanical and magnetic properties of the high-entropy alloy can be further adjusted by adjusting the heat treatment conditions.The method is simple and easy to operate, and can be widely applied to the preparation of various high-entropy alloys, with wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to an alloy and a preparation method thereof, and particularly relates to a FCC+BCC dual-phase soft magnetic high-entropy alloy and a preparation method thereof. BACKGROUND

[0002] High-entropy alloys are usually formed by five or more than five kinds of metals with equal or relative proportions. In recent years, high-entropy alloys have attracted extensive attention due to their excellent mechanical properties, physical properties, corrosion resistance and radiation resistance. Recent studies have shown that multi-principal element alloys with a large atomic ratio difference also have excellent properties of high-entropy alloys. Soft magnetic materials are key components of social intelligence and are widely used in energy storage, power transmission, photovoltaics, new energy, 6G mobile communication technology (6G), household appliances and other fields. They also have broad application prospects in the fields of high-end electrical and industrial intelligence, cloud computing, Internet of Things and other new infrastructure construction characterized by high frequency, high power and miniaturization. The commonly used soft magnetic materials, such as low-carbon steel, silicon steel sheet, permalloy and ferrite, have problems such as high eddy current loss, poor high-temperature microstructure stability, low service temperature and complex preparation process. High-entropy alloys have a wide composition design space and controllable microstructure, which can make the materials have excellent soft magnetic properties while meeting the requirements of low loss, corrosion resistance and high-temperature oxidation resistance under complex conditions. At present, the international situation is complex and changing, and it is of great strategic significance to develop and promote new high-entropy alloy materials with independent intellectual property rights. However, the research on high-entropy alloys at home and abroad mainly focuses on theoretical academic research, and the industrial application in the field of equipment is still in its infancy. Therefore, high-entropy alloys have great application prospects in the field of soft magnetic materials. SUMMARY

[0003] The purpose of the present application is to provide a dual-phase soft magnetic high-entropy alloy with high strength and good magnetic properties, and a preparation method of the dual-phase soft magnetic high-entropy alloy.

[0004] The technical scheme of the present application is as follows: The present application relates to a dual-phase soft magnetic high-entropy alloy, which is composed of Fe, Co, Cr and V, has FCC and BCC dual phases, the FCC phase is rich in Co, Cr and V, and the BCC phase is rich in Fe.

[0005] Preferably, the element composition of the dual-phase high-entropy alloy is as follows: Fe: 40-53 at.%, Co: 35-40 at.%, V: 10-15 at.%, and Cr: 2-5 at.%.

[0006] In another aspect, the present application provides a preparation method of a dual-phase soft magnetic high-entropy alloy, which comprises the following steps:

[0007] (1) Design of dual-phase high-entropy alloy: determine the element composition of the dual-phase high-entropy alloy as follows: Fe: 40-53 at.%, Co: 35-40 at.%, V: 10-15 at.%, Cr: 2-5 at.%;

[0008] (2) Preparation of alloy: according to the element composition of the dual-phase high-entropy alloy, the corresponding mass of Fe, Co, Cr and V is weighed, and the high-entropy alloy ingot is obtained by melting and pouring;

[0009] (3) Homogenization treatment: the high-entropy alloy ingot of the above step is subjected to homogenization treatment to obtain the high-entropy alloy ingot after homogenization treatment:

[0010] (4) Controlled cold rolling: the high-entropy alloy ingot after homogenization treatment is made into high-entropy alloy plate;

[0011] (5) Two-stage isothermal treatment: the high-entropy alloy plate prepared in the above step is subjected to two-stage isothermal treatment: ① first heat treatment, temperature 900-1050℃, holding time 1-5min, water cooling; this temperature range completes recovery recrystallization, eliminates deformed structure, and obtains equiaxed crystals; ② second isothermal treatment, the sample after the first heat treatment is used as the sample for the second isothermal treatment, the temperature is set to 550-800℃, and the holding time is 30min-4h; through this treatment, the phase volume fraction control is realized; the dual-phase soft magnetic high-entropy alloy is obtained through the two-stage isothermal treatment.

[0012] Further, in step (2), the preparation of the alloy specifically includes:

[0013] The high-purity Fe, Co, Cr and V blocks are placed in a vacuum induction floating melting furnace, vacuum is pumped and argon is injected, the current is adjusted to 200-500A, the block metal is completely melted into liquid state, the magnetic stirring is started and maintained for 5-10min, the metal liquid is poured into a mold to cool into an ingot, and the high-entropy alloy ingot is obtained.

[0014] Further, in step (3), the homogenization treatment specifically includes:

[0015] The ingot is placed in a tube furnace, vacuum is pumped, argon is filled, the furnace temperature is set to 1000-1200℃, and the sample is quickly put into water for quenching after a certain holding time, so that the elements in the ingot are uniformly distributed.

[0016] Preferably, the holding time is 12-24h.

[0017] Further, in step (4), the controlled cold rolling specifically comprises: cutting the high-entropy alloy ingot after uniform treatment into a square block by using a wire cutting method, and rolling the high-entropy alloy ingot by using a roller mill in multiple passes, wherein the downward displacement of each pass is 0.1-0.5 mm, and the deformation amount is controlled to be 70-80%, so as to obtain the high-entropy alloy plate.

[0018] Preferably, in step (4), the roller speed of the roller mill is 200-400 r / min.

[0019] Preferably, in step (4), the thickness of the high-entropy alloy plate is 2-3 mm.

[0020] In the above technical method, the dual-phase soft magnetic high-entropy alloy has a high saturation magnetization (50-200 emu / g), a low coercivity (50-100 Oe), a high tensile yield strength (800-2000 MPa), and a moderate plasticity (10-30%).

[0021] The preparation principle of the present application is that metal elements are selected, and a part of residual austenite (FCC phase) is reserved between martensite phases (BCC phases) in the high-entropy alloy by using a suitable heat treatment process, so as to effectively improve the plasticity of the alloy while keeping the magnetic property and strength of the alloy.

[0022] In the preparation process of the present application, plastic deformation and heat treatment processes have a decisive influence on the microstructure of the high-entropy alloy. Cold rolling changes the grain size of the material; the first heat treatment at a temperature of 900-1050 ℃ for 1-5 min completes recovery and recrystallization, eliminates the deformed structure, and obtains an equiaxed crystal process; and the second isothermal treatment at a temperature of 550-800 ℃ for 30 min-4 h realizes the control of phase volume fraction. By adjusting the conditions of plastic deformation and heat treatment, the phase composition of the alloy can be further adjusted, and the mechanical and physical properties can be improved.

[0023] Advantages: Compared with the prior art, the present application has the following advantages:

[0024] (1) The present application prepares a novel dual-phase soft magnetic high-entropy alloy by reasonable component design and matched reaction temperature range, and the microstructure is a pearlitic lamellar structure composed of alternating FCC austenite and BCC martensite lamellas;

[0025] (2) The preparation method of the present application is simple, has low cost, and is easy to industrialize and popularize;

[0026] (3) The high-copper eutectic multi-principal element alloy obtained by the method has good magnetic and mechanical properties. The saturation magnetization of the alloy is between 50emu / g and 200emu / g, the tensile strength is up to 2000MPa, the minimum is about 800MPa, and the plasticity is between 10% and 30%. The comprehensive performance of the alloy reaches the advanced level at present, and is expected to be applied to the industrial production of soft magnetic materials. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is an SEM image of the cold-rolled sample in Comparative Example 1 after one-stage heat treatment;

[0028] Figure 2 is an EBSD phase distribution map of the cold-rolled sample in Example 1 after two-stage heat treatment;

[0029] Figure 3 is an EDS element distribution map of the cold-rolled sample in Example 2 after two-stage heat treatment;

[0030] Figure 4 is a phase composition and saturation magnetization change map of the cold-rolled sample in Example 2 after two-stage heat treatment. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be further described below in combination with the drawings.

[0032] Comparative Example 1

[0033] The present comparative example provides a preparation method of a high-entropy alloy, which specifically comprises:

[0034] (1) Alloy design based on phase diagram: selecting metal elements, determining the element composition of the dual-phase high-entropy alloy as Fe: 44.5at.%, Co: 38.9at.%, V: 13.3at.%, Cr: 3.3at.%.

[0035] (2) Melting and pouring: according to the theoretically calculated alloy composition, the raw materials with a purity of more than 99.99% are weighed and put into a vacuum induction melting furnace, vacuum is extracted to a gas pressure of less than 5×10 -4 Pa, then the magnetic stirring is opened, the melting current is set to 300A for 10min, the metal liquid is quickly poured into a mold to cool into an ingot.

[0036] (3) Homogenization treatment: the ingot is placed in a tube furnace, under a high-purity argon atmosphere, after being kept at 1150℃ for 12h, it is rapidly quenched.

[0037] (4) Controlled cold rolling: a 100T double-roller rolling mill is used, the roller speed of the rolling mill is 300r / min, and the rolling amount is controlled at 80%.

[0038] Referring to Figure 1 , the sample after cold rolling and recrystallization shows obvious relief under SEM, indicating that the sample after 1000℃, 2min rapid heat treatment has a structure of martensite.

[0039] Example 1

[0040] The embodiment provides a dual-phase soft magnetic high-entropy alloy, which is composed of Fe, Co, Cr and V four elements, has an FCC and BCC dual-phase, the FCC phase is rich in Co, Cr and V, and the BCC phase is rich in Fe.

[0041] The embodiment provides a preparation method of a dual-phase soft magnetic high-entropy alloy, and specifically comprises the following steps:

[0042] (1) Alloy design based on phase diagram: selecting metal elements, and determining the element composition of the dual-phase high-entropy alloy as Fe: 44.5at.%, Co: 38.9at.%, V: 13.3at.% and Cr: 3.3at.%.

[0043] (2) Melting and pouring: according to the calculated alloy composition, the raw materials with a purity greater than 99.99% are weighed and placed in a vacuum induction melting furnace, vacuum is extracted to a pressure lower than 5×10 -4 Pa, then the magnetic stirring is opened, the melting current is set to 300A for 10min, the metal liquid is quickly poured into a mold to cool into an ingot.

[0044] (4) Controlled cold rolling: a 100T double-roller mill is used, the roller speed of the mill is 300r / min, and the rolling amount is controlled to be 80%.

[0045] (5) Isothermal treatment: first, the sample is placed in a 1000℃ tube furnace for rapid heat treatment for 2min and immediately quenched, then the sample after the first heat treatment is placed in a 600℃ tube furnace for heat preservation for 1h and quenching,

[0046] for the second isothermal treatment.

[0047] Referring to Figure 2 , the EBSD of the sample shows that the sample has an FCC and BCC dual-phase, and the two phases form a pearlite-like structure alternately in a layered and lamellar form. The tensile test shows that the material has a relatively high tensile yield strength, reaching about 2000MPa, and also has good ductility, with a plasticity of 10%.

[0048] Example 2

[0049] The embodiment provides a preparation method of a dual-phase soft magnetic high-entropy alloy, and specifically comprises the following steps:

[0050] (1) Alloy design based on a phase diagram: metal elements are selected, and element composition of the dual-phase high-entropy alloy is determined as Fe: 40 at.%, Co: 40 at.%, V: 15 at.%, and Cr: 5 at.%.

[0051] (2) Melting and pouring: according to the theoretically calculated alloy composition, raw materials with a purity greater than 99.99% are weighed and placed in a vacuum induction melting furnace, vacuum is drawn to an air pressure lower than 5*10 -4 Pa, magnetic stirring is started, a melting current is set to 300 A and maintained for 10 min, the metal liquid is quickly poured into a mold to cool into an ingot. (3) Homogenization treatment: the ingot is placed in a tube furnace, under a high-purity argon atmosphere, and kept at 1150 DEG C for 12 h and then rapidly quenched.

[0052] (4) Controlled cold rolling: a 100T double-roller rolling mill is used, the roller speed of the rolling mill is 300 r / min, and the rolling amount is controlled to be 80%.

[0053] (5) Isothermal treatment: first, the sample is placed in a tube furnace at 1000 DEG C for rapid heat treatment for 2 min and immediately quenched, then the sample after the first heat treatment is placed in a tube furnace at 700 DEG C for heat preservation for 2 h and quenched,

[0054] for the second isothermal treatment.

[0055] Embodiment 3

[0056] The embodiment provides a preparation method of a dual-phase soft magnetic high-entropy alloy, and specifically comprises the following steps:

[0057] (1) Alloy design based on a phase diagram: metal elements are selected, and element composition of the dual-phase high-entropy alloy is determined as Fe: 40 at.%, Co: 40 at.%, V: 15 at.%, and Cr: 5 at.%.

[0058] (2) Melting and pouring: according to the theoretically calculated alloy composition, raw materials with a purity greater than 99.99% are weighed and placed in a vacuum induction melting furnace, vacuum is drawn to an air pressure lower than 5*10 -4 Pa, magnetic stirring is started, a melting current is set to 300 A and maintained for 10 min, the metal liquid is quickly poured into a mold to cool into an ingot. (3) Homogenization treatment: the ingot is placed in a tube furnace, under a high-purity argon atmosphere, and kept at 1150 DEG C for 12 h and then rapidly quenched.

[0059] (4) Controlled cold rolling: a 100T double-roller rolling mill is used, the roller speed of the rolling mill is 300 r / min, and the rolling amount is controlled to be 80%.

[0060] (5) Isothermal treatment: first, the sample is placed in a tube furnace at 1000℃ for rapid heat treatment for 2min and immediately quenched, then the sample after the first heat treatment is placed in a tube furnace at 700℃ for 2h and quenched,

[0061] A second isothermal treatment is performed.

[0062] Referring to Figure 3 EDS surface scanning of the sample shows that the FCC phase is rich in Co, Cr and V, and the BCC phase is rich in Fe. Within the composition range of the claim, the experimental surface sample organization and element distribution are consistent, so the research content and method are the same.

[0063] Example 4

[0064] The embodiment provides a preparation method of a dual-phase soft magnetic high-entropy alloy, which is different from example 1 in that in step (5), the second isothermal treatment is performed at 550℃ in a tube furnace for 1h, and then quenched. The remaining steps are the same as those in example 1. Tensile test shows that the tensile yield strength of the material is about 1000MPa.

[0065] Example 5

[0066] The embodiment provides a preparation method of a dual-phase soft magnetic high-entropy alloy, which is different from example 1 in that in step (5), the second isothermal treatment is performed at 700℃ in a tube furnace for 1h, and then quenched. The remaining steps are the same as those in example 1. Tensile test shows that the tensile yield strength of the material is about 1200MPa, and the plasticity reaches 20%.

[0067] Example 6

[0068] The embodiment provides a preparation method of a dual-phase soft magnetic high-entropy alloy, which is different from example 1 in that in step (5), the second isothermal treatment is performed at 800℃ in a tube furnace for 1h, and then quenched. The remaining steps are the same as those in example 1. Tensile test shows that the tensile yield strength of the material is about 1050MPa, and the plasticity reaches 20%.

[0069] Referring to Figure 4, the phase composition and magnetic properties of the alloy changed accordingly after different heat treatments. The saturation magnetization of the alloy reached 50-200 emu / g, while the coercivity was controlled below 100 Oe, with good magnetic properties. According to the experimental characterization experiments (metallographic experiment, XRD analysis, SEM characterization), mechanical experiments (hardness experiment, tensile experiment), and magnetic properties (VSM experiment) data, the organization and performance of the sample are mainly related to the temperature of the second isothermal treatment, and the treatment time has less effect. For the 700℃, 1h sample, it can be inferred that the performance of the sample with different holding times at 700℃, 30min and 700℃, 4h is similar. In the temperature range of the second isothermal treatment in the claim, compared with other samples, the mechanical properties of the sample of 600℃, 1h are the best.

[0070] Example 7

[0071] (1) Phase diagram-based alloy design: Select metal elements and determine the element composition of the dual-phase high-entropy alloy as Fe: 44.5at.%, Co: 38.9at.%, V: 13.3at.%, Cr: 3.3at.%.

[0072] (2) Melting and pouring: According to the calculated alloy composition, weigh the raw materials with a purity of more than 99.99% and put them into a vacuum induction melting furnace. After the vacuum is extracted to a pressure below 5×10 -4 Pa, open the magnetic stirrer, set the melting current to 500A for 5min, and quickly pour the metal liquid into the mold to cool into an ingot.

[0073] (3) Homogenization treatment: Place the ingot in a tube furnace under a high-purity argon atmosphere, heat at 1000℃ for 24h, and then quench rapidly.

[0074] (4) Controlled cold rolling: Use a 100T double-roller rolling mill with a roller speed of 200r / min and a rolling amount controlled at 70%.

[0075] (5) Isothermal treatment: First, heat the sample at 900℃ in a tube furnace for 5min and immediately quench, then place the sample after the first heat treatment at 700℃ in a tube furnace for 30min and quench, and perform the second isothermal treatment.

[0076] Tensile test shows that the tensile yield strength of the material is about 1200MPa.

[0077] Example 8

[0078] (1) Phase diagram-based alloy design: Select metal elements and determine the element composition of the dual-phase high-entropy alloy as Fe: 44.5at.%, Co: 38.9at.%, V: 13.3at.%, Cr: 3.3at.%.

[0079] (2) Melting and pouring: According to the calculated alloy composition, raw materials with purity greater than 99.99% were weighed and put into a vacuum induction melting furnace, vacuum was extracted to an air pressure lower than 5x10 -4 Pa, the magnetic stirring was opened, the melting current was set to 200A for 10 min, the metal liquid was quickly poured into a mold to cool into an ingot. (3) Homogenization treatment: the ingot was placed in a tube furnace, under a high-purity argon atmosphere, 1200°C for 12h, then rapidly quenched.

[0080] (4) Controlled cold rolling: a 100T double-roller rolling mill was used, the roller speed of the rolling mill was 400r / min, the rolling amount was controlled at 80%.

[0081] (5) Isothermal treatment: first, the sample was placed in a tube furnace at 1050°C for rapid heat treatment for 1 min and immediately quenched, then the sample after the first heat treatment was placed in a tube furnace at 700°C for 4h and quenched, for the second isothermal treatment.

[0082] Tensile test showed that the tensile yield strength of the material was about 1200MPa.

Claims

1. A two-phase soft magnetic high-entropy alloy, characterized in that, This high-entropy alloy is composed of four elements: Fe, Co, Cr, and V. It has two phases: FCC and BCC. The FCC phase is rich in Co, Cr, and V, while the BCC phase is rich in Fe. The two phases are layered and lamellar, alternating to form a pearlite-like structure. The elemental composition of the two-phase high-entropy alloy is: Fe: 40~53 at. %, Co: 35~40 at. %, V: 10~15 at. %, Cr: 2~5 at. %.

2. A method for preparing the dual-phase soft magnetic high-entropy alloy according to claim 1, characterized in that, Includes the following steps: (1) Design of dual-phase high-entropy alloy: The elemental composition of the dual-phase high-entropy alloy was determined to be: Fe: 40~53 at.%, Co: 35~40 at.%, V: 10~15 at.%, Cr: 2~5 at.%% (2) Alloy preparation: Fe, Co, Cr and V of corresponding mass are weighed according to the elemental composition of the dual-phase high-entropy alloy, and high-entropy alloy ingots are obtained by melting and casting. (3) Homogenization treatment: The high-entropy alloy ingots in the above steps are subjected to homogenization treatment to obtain homogenized high-entropy alloy ingots: (4) Controlled cold rolling: The homogenized high-entropy alloy ingot is made into high-entropy alloy sheet; (5) Two-stage isothermal treatment: The high-entropy alloy plate obtained in the above steps is subjected to two-stage isothermal treatment: ① First-stage heat treatment, temperature 900~1050 ℃, holding time 1~5 min, water cooling; the temperature range completes the recovery recrystallization, eliminates the deformed structure, and obtains equiaxed crystals. ② Secondary isothermal treatment: The sample after primary heat treatment is used as the sample for secondary isothermal treatment. The temperature is set at 550~800 ℃ and the holding time is 30 min~4 h. Through this treatment, the phase volume fraction is controlled. A two-phase soft magnetic high-entropy alloy is obtained through two-stage isothermal treatment.

3. The method for preparing a dual-phase soft magnetic high-entropy alloy according to claim 2, characterized in that, In step (2), the preparation of the alloy specifically includes: High-purity Fe, Co, Cr and V blocks are placed in a vacuum induction levitation melting furnace, argon gas is introduced into the vacuum, and the current is adjusted to 200~500 A. After the block metal is completely melted into a liquid state, magnetic stirring is started and maintained for 5~10 minutes. The molten metal is then poured into a mold to cool into an ingot, thus obtaining a high-entropy alloy ingot.

4. The method for preparing a dual-phase soft magnetic high-entropy alloy according to claim 2, characterized in that, In step (3), the homogenization process specifically includes: The ingot was placed in a tube furnace, evacuated, and filled with argon gas. The furnace temperature was set to 1000~1200 ℃ and held for 12~24 h. Finally, the furnace was opened, and the sample was quickly placed in water for quenching to ensure that the elements in the ingot were evenly distributed.

5. The method for preparing the dual-phase soft magnetic high-entropy alloy according to claim 2, characterized in that, In step (4), controlling cold rolling specifically includes: using wire cutting to cut the uniformly treated high-entropy alloy ingot into blocks, using a rolling mill for multi-pass rolling, with a pressing amount of 0.1~0.5 mm per pass, and controlling the deformation amount to 70~80%, thereby obtaining high-entropy alloy sheet.

6. The method for preparing the dual-phase soft magnetic high-entropy alloy according to claim 5, characterized in that, In step (4), the roll speed of the rolling mill is 200~400 r / min.

7. The method for preparing the dual-phase soft magnetic high-entropy alloy according to claim 2 or 5, characterized in that, In step (4), the thickness of the high-entropy alloy plate is 2~3 mm.

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