A high-tenacity, hydrogen embrittlement-resistant Nb micro-alloyed high-entropy alloy and a preparation method thereof

Abstract

The application discloses a high-toughness and hydrogen embrittlement resistant Nb micro-alloyed high-entropy alloy and a preparation method thereof. According to atomic percentage, the chemical composition of the high-entropy alloy comprises the following components: C: 0.2-0.6%, Nb: 0.05-0.1%, Mn: 28-33%, Co: 9-11%, Cr: 9-11%, and the balance of Fe and other inevitable impurities. The preparation method of the high-entropy alloy comprises the following steps: S1, melting to obtain a high-entropy alloy ingot; S2, high-temperature rolling: the high-entropy alloy ingot is placed into a high-temperature furnace and heated to 900-1000 DEG C and kept for 8-12 min, and then multi-pass rolling is carried out with a total reduction of 50-60%; S3, homogenization heat treatment: the treatment temperature is 1200-1250 DEG C, the treatment time is 2-4 h, and then water quenching is carried out to room temperature; S4, room temperature cold rolling: multi-pass cold rolling is carried out at room temperature with a total reduction of 50%; and S5, recrystallization annealing: the recrystallization annealing treatment temperature is 750-900 DEG C, the treatment time is 10-30 min, and then water quenching is carried out to room temperature, and the high-entropy alloy is obtained. The high-entropy alloy realizes the simultaneous improvement of strength and hydrogen embrittlement resistance through Nb micro-alloying and microstructure regulation.

Description

TECHNICAL FIELD

[0001] The application relates to a Nb micro-alloyed high-entropy alloy with high strength and toughness and hydrogen embrittlement resistance, and belongs to the technical field of metal materials. BACKGROUND

[0002] Large-scale application of hydrogen energy has important strategic significance for solving energy crisis, environmental problems and realizing sustainable development. Hydrogen gas is compressed by high pressure for storage, transportation and refueling, which is the most widely used hydrogen energy utilization method at present, and the main bearing structure is a metal material system. Hydrogen is easy to diffuse into metal materials, and metal materials in a hydrogen environment for a long time will have hydrogen embrittlement problems such as reduction of strength and toughness and acceleration of crack propagation, and these problems will be more prominent as the pressure increases. In order to further increase the hydrogen storage volume density, it is necessary to increase the hydrogen pressure, which urgently requires the development of metal structure materials with higher strength and hydrogen embrittlement resistance. However, the increase of material strength often accompanies the increase of hydrogen embrittlement sensitivity, and this contradiction is one of the main challenges in the development of hydrogen embrittlement resistant materials.

[0003] The transition metal high-entropy alloy with multiple main elements has excellent hydrogen compatibility due to the strong local chemical environment fluctuation and lattice distortion in the crystal. The composition design of multiple main elements enables it to couple multiple strengthening mechanisms and has excellent strength and plasticity matching. Among them, the non-equiatomic ratio FeMnCoCr-C interstitial metastable high-entropy alloy exhibits phase transformation-twinning induced plasticity, interstitial strengthening and precipitation strengthening and other mechanisms during tensile process, and has good strength and plasticity matching and certain hydrogen embrittlement resistance. However, since the grain boundary itself is a reversible hydrogen trap with a high hydrogen diffusion coefficient, the phase transformation and twinning impact the grain boundary to form micro stress concentration, which further promotes the local enrichment of hydrogen and forms intergranular cracking, which limits the further improvement of the hydrogen embrittlement resistance. SUMMARY

[0004] The application aims to solve the technical problems in the prior art and provide a Nb micro-alloyed high-entropy alloy with high strength and toughness and hydrogen embrittlement resistance. The high-entropy alloy realizes the simultaneous improvement of strength and hydrogen embrittlement resistance through Nb micro-alloying and microstructure regulation.

[0005] The technical features adopted by the application to achieve the application purpose are: 1. A Nb micro-alloyed high-entropy alloy with high strength and toughness and hydrogen embrittlement resistance, characterized in that the chemical composition of the high-entropy alloy is: C: 0.2-0.6%, Nb: 0.05-0.1%, Mn: 28-33%, Co: 9-11%, Cr: 9-11%, and the balance is Fe and other inevitable impurities.

[0006] Further, the high-entropy alloy according to the application contains 30% of Mn, 10% of Co and 10% of Cr in terms of atomic percentage.

[0007] Further, the high-entropy alloy according to the present application has a content of C of 0.3-0.5% in terms of atomic percentage.

[0008] Further, the microstructure of the high-entropy alloy according to the present application is composed of an austenite matrix, and the nanometer NbC precipitates are dispersedly distributed in the matrix and at the grain boundaries, and the phase interface between the NbC precipitates and the austenite matrix is semi-coherent.

[0009] A preparation method of the high-entropy alloy with high strength and toughness and hydrogen embrittlement resistance according to the present application, which comprises the following steps:

[0010] S1, melting: raw materials are prepared according to the chemical composition of the high-entropy alloy in terms of atomic percentage, and the prepared raw materials are placed in a vacuum induction furnace for melting, the melting temperature is 1400-1500℃, after sufficient melting for 10-15min, the temperature is lowered to 1350-1450℃ for pouring into ingots, and the melting process is repeated for 4-5 times, and finally the high-entropy alloy ingot is poured;

[0011] S2, high-temperature rolling: the high-entropy alloy ingot is placed in a high-temperature furnace and heated to 900-1000℃ for 8-12min, and then multi-pass rolling is performed with a total reduction of 50-60% to obtain a high-entropy alloy plate;

[0012] S3, homogenization heat treatment: the high-temperature rolled high-entropy alloy plate is subjected to homogenization heat treatment at a temperature of 1200-1250℃ for 2-4h, and then water quenched to room temperature;

[0013] S4, room temperature cold rolling: the high-entropy alloy plate after homogenization heat treatment is subjected to multi-pass cold rolling at room temperature with a total reduction of 50%;

[0014] S5, recrystallization annealing: the cold-rolled high-entropy alloy plate is subjected to recrystallization annealing heat treatment at a temperature of 750-900℃ for 10-30min, and then water quenched to room temperature to obtain the high-entropy alloy with high strength and toughness and hydrogen embrittlement resistance.

[0015] Further, before the prepared raw materials are placed in the vacuum induction furnace for melting in step S1 of the preparation method according to the present application, an in-furnace gas washing operation is performed, which specifically comprises the following steps: -5 After the vacuum degree is less than 1×10 -0.5MPa, the second vacuum gas washing operation is performed after standing for 15min, and this process is repeated for 3 times.

[0016] Further, in the high-temperature rolling in step S2 of the preparation method according to the present application, 7-9 passes of rolling are performed.

[0017] Further, the step S4 of the preparation method of the present application is cold rolling at room temperature for 5-7 passes.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] (1) The high-entropy alloy involved in the present application is made of Fe, Mn, Cr, Co, Nb and C, and the raw materials are easy to obtain and the purity is easy to achieve.

[0020] (2) The high-entropy alloy of the present application is added with 0.05-0.1% of Nb and 0.2-0.6% of C in atomic percentage, so that fine NbC precipitates are dispersedly distributed in the single-phase austenite matrix of the high-entropy alloy, which has excellent hydrogen embrittlement resistance and good strength-plasticity matching characteristics, with a tensile strength higher than 1000 MPa and an elongation after fracture greater than 45%.

[0021] (3) The preparation method of the material is vacuum induction melting, rolling and heat treatment, which is simple to realize, has large production size and is suitable for industrial production, and has high economic value. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Figure 1 is a TEM microstructure morphology diagram of the high-entropy alloy of Example 1 of the present application.

[0023] Figure 2 Figure 2 is a comparison diagram of tensile engineering stress-strain curves of the high-entropy alloy of Example 1 of the present application and the high-entropy alloys of Comparative Example 1 and Comparative Example 2 under room temperature non-hydrogen-charged air environment and in-situ electrochemical hydrogen charging.

[0024] Figure 3 Figure 3 is a comparison diagram of tensile engineering stress-strain curves of the high-entropy alloy of Example 3 of the present application and the high-entropy alloy of Comparative Example 1 under room temperature non-hydrogen-charged air environment and in-situ electrochemical hydrogen charging. DETAILED DESCRIPTION

[0025] Example 1

[0026] A high-tenacity, hydrogen embrittlement-resistant Nb micro-alloyed high-entropy alloy, according to atomic percentage, the chemical composition of the high-entropy alloy is: Fe: 49.45%, Mn: 30%, Co: 10%, Cr: 10%, C: 0.5%, Nb: 0.05%; the microstructure of the high-entropy alloy is composed of an austenite matrix, with nanometer NbC precipitates dispersedly distributed in the crystal and the grain boundary, and the phase interface between the NbC precipitates and the austenite matrix is semi-coherent.

[0027] The high-tenacity, hydrogen embrittlement-resistant Nb micro-alloyed high-entropy alloy of the present example is denoted as Fe 49.45 Mn 30Co 10 Cr 10 Nb 0.05 C 0.5 , the preparation method steps are as follows:

[0028] S1, smelting: raw materials are prepared according to the atomic percentage of the chemical composition of the high-entropy alloy, the raw materials are Mn electrolytic sheet, Cr electrolytic sheet, Fe electrolytic sheet, Co block, Nb block and graphite with a purity of not less than 99.9%; the prepared raw materials are placed in a vacuum induction furnace for smelting, and before smelting, an in-furnace gas washing operation is first performed: the furnace is vacuumized, and when the vacuum degree is less than 1x10 -5 -5 MPa, argon with a purity of 99.9% is filled, and when the pressure in the furnace reaches-0.5 MPa, the gas filling is stopped, and after standing for 15 min, a second vacuum gas washing operation is performed, and this process is repeated for a total of 3 times, and after the gas washing is completed, vacuum smelting is performed; the smelting temperature is 1500℃, and after fully melting for 10 min, the temperature is lowered to 1450℃ for casting into ingots, and the smelting process is repeated for 5 times, and finally the high-entropy alloy ingots with a thickness of 20 mm are cast;

[0029] S2, high-temperature rolling: the high-entropy alloy ingots are placed in a high-temperature furnace and heated to 900℃, and then 8 passes of rolling are performed with a total reduction of 50%, and a plate with a thickness of 10 mm is obtained;

[0030] S3, homogenization heat treatment: the high-entropy alloy plate after high-temperature rolling is subjected to homogenization heat treatment, the heat treatment temperature is 1200℃, and the treatment time is 2h, and then water quenching to room temperature;

[0031] S4, room temperature cold rolling: the plate after homogenization heat treatment is subjected to multi-pass cold rolling at room temperature, each pass is reduced by 1mm, and the rolling speed is 0.4s -1 , and finally a plate with a thickness of 5mm is obtained; the total reduction is 50%;

[0032] S5, recrystallization annealing: the cold-rolled plate is subjected to recrystallization annealing heat treatment, the treatment temperature is 850℃, and the treatment time is 30min, and then water quenching to room temperature, thereby obtaining the high-strength and high-toughness Nb micro-alloyed high-entropy alloy with hydrogen embrittlement resistance.

[0033] Figure 1 It is a TEM morphology diagram of the microstructure of the high-entropy alloy of the present embodiment. As can be seen from the figure, the microstructure of the high-entropy alloy is austenitic matrix and dispersedly distributed nanometer NbC particles (black particles in the figure), the interface between NbC and the matrix is semi-coherent, the grain size of the alloy is about 8.2μm, and the size of NbC is about 8.6nm.

[0034] Example Two

[0035] A high-strength, high-toughness, and hydrogen-embrittlement-resistant Nb microalloyed high-entropy alloy has the following chemical composition by atomic percentage: Fe: 48.62%, Mn: 31%, Co: 10%, Cr: 10%, C: 0.3%, Nb: 0.08%. The microstructure of the high-entropy alloy consists of an austenitic matrix with dispersed nano-NbC precipitates within the grains and at the grain boundaries. The NbC precipitates and the austenitic matrix exhibit a semi-coherent phase interface.

[0036] In this embodiment, the high-strength, tough, and hydrogen-embrittle-resistant Nb microalloyed high-entropy alloy is denoted as Fe. 48.62 Mn 31 Co 10 Cr 10 Nb 0.08 C 0.3 The preparation method steps are as follows:

[0037] S1. Melting: Prepare raw materials according to the atomic percentage of the chemical composition of the high-entropy alloy. The raw materials are Mn electrolytic sheets, Cr electrolytic sheets, Fe electrolytic sheets, Co blocks, Nb blocks, and graphite with a purity of not less than 99.9%. Place the prepared raw materials in a vacuum induction furnace for melting. Before melting, perform a furnace cleaning operation: evacuate the furnace until the vacuum degree is less than 1×10⁻⁶. -5 Argon gas with a purity of 99.9% was then introduced. When the pressure inside the furnace reached -0.5MPa, the gas introduction was stopped. After standing for 15 minutes, a second vacuum cleaning operation was performed. This process was repeated 3 times. After the cleaning was completed, vacuum melting was carried out. The melting temperature was 1480℃. After melting for 15 minutes, the temperature was lowered to 1400℃ and poured into an ingot. The melting process was repeated 5 times, and finally a high-entropy alloy ingot with a thickness of 20mm was cast.

[0038] S2. High-temperature rolling: The high-entropy alloy ingot is placed in a high-temperature furnace, heated to 900°C, held for 10 minutes, and then rolled in 8 passes with a total reduction of 50% to obtain a plate with a thickness of 10 mm.

[0039] S3. Homogenization heat treatment: The high-entropy alloy sheet rolled at high temperature is subjected to homogenization heat treatment at a temperature of 1200℃ for 2 hours, and then water quenched to room temperature.

[0040] S4. Room Temperature Cold Rolling: The homogenized heat-treated sheet material is subjected to multiple cold rolling passes at room temperature, with each pass reducing the thickness by 0.8 mm and the rolling speed being 0.5 s. -1 The final product is a 5mm thick sheet; the total pressing amount is 50%.

[0041] S5, recrystallization annealing: the cold-rolled plate is subjected to recrystallization annealing heat treatment, the treatment temperature is 900 DEG C, the treatment time is 15 min, and then water quenching to room temperature, thereby obtaining the high-strength and high-toughness Nb micro-alloyed high-entropy alloy with hydrogen embrittlement resistance.

[0042] The microstructure of the high-entropy alloy of the embodiment is observed by transmission electron microscopy, and the microstructure of the high-entropy alloy of the embodiment is an austenitic matrix and dispersedly distributed nanometer NbC particles, the interface between the NbC and the matrix is semi-coherent, the grain size of the alloy is about 9.7 mu m, and the size of the NbC is about 7.3 nm.

[0043] Example three

[0044] A high-strength and high-toughness Nb micro-alloyed high-entropy alloy with hydrogen embrittlement resistance, according to atomic percentage, the chemical composition of the high-entropy alloy is: Fe: 49.4%, Mn: 30%, Co: 10%, Cr: 10%, C: 0.5%, Nb: 0.1%; the microstructure of the high-entropy alloy is composed of an austenitic matrix, nanometer NbC precipitates are dispersedly distributed in the grain and the grain boundary, and the interface between the NbC precipitates and the austenitic matrix is semi-coherent.

[0045] The high-strength and high-toughness Nb micro-alloyed high-entropy alloy of the embodiment is denoted as Fe 49.4 Mn 30 Co 10 Cr 10 Nb 0.1 C 0.5 , and the preparation method steps are as follows:

[0046] S1, smelting: preparing raw materials according to the atomic percentage of the chemical composition of the high-entropy alloy, the raw materials are Mn electrolytic sheet, Cr electrolytic sheet, Fe electrolytic sheet, Co block, Nb block and graphite with a purity of not less than 99.9%; placing the prepared raw materials in a vacuum induction furnace for smelting, first performing in-furnace gas washing operation before smelting: vacuumizing the furnace, and when the vacuum degree is less than 1*10 -5 After that, 99.9% pure argon is filled, and when the pressure in the furnace reaches-0.5 MPa, the gas filling is stopped, and after standing for 15 min, the second vacuum gas washing operation is performed, and the process is repeated for 3 times, and after the gas washing is completed, vacuum smelting is performed; the smelting temperature is 1480 DEG C, after fully melting for 15 min, the temperature is lowered to 1400 DEG C, and the ingot is poured, and the smelting process is repeated for 5 times, and finally the high-entropy alloy ingot with a thickness of 20 mm is poured;

[0047] S2, high-temperature rolling: placing the high-entropy alloy ingot into a high-temperature furnace, heating to 900 DEG C, holding for 10 min, and then rolling for 8 passes, with a total reduction of 50%, to obtain a plate with a thickness of 10 mm;

[0048] S3, homogenization heat treatment: the high-temperature rolled high-entropy alloy plate is subjected to homogenization heat treatment, the heat treatment temperature is 1200℃, the treatment time is 2h, and then water quenching is performed to room temperature;

[0049] S4, room temperature cold rolling: the plate after the homogenization heat treatment is subjected to multi-pass cold rolling at room temperature, the thickness of each pass is 0.8mm, and the rolling speed is 0.5s -1 , and finally the plate with a thickness of 5mm is obtained; the total thickness reduction is 50%;

[0050] S5, recrystallization annealing: the cold-rolled plate is subjected to recrystallization annealing heat treatment, the treatment temperature is 850℃, the treatment time is 30min, and then water quenching is performed to room temperature, thereby the high-entropy alloy with high strength and toughness and hydrogen embrittlement resistance is prepared.

[0051] The microstructure of the high-entropy alloy of the embodiment is observed by a transmission electron microscope, the microstructure of the high-entropy alloy of the embodiment is austenite matrix and dispersedly distributed nanometer NbC particles, the interface between the NbC and the matrix is semi-coherent, the grain size of the alloy is about 7.2μm, and the size of the NbC is about 9.3nm.

[0052] Comparative Example One

[0053] An FeMnCoCrC high-entropy alloy, according to atomic percentage, the chemical composition of the high-entropy alloy is: Fe: 48.5%, Mn: 30%, Co: 10%, Cr: 10%, and C: 0.5%.

[0054] The high-entropy alloy of the comparative example is denoted as Fe 48.5 Mn 30 Co 10 Cr 10 C 0.5 , and the preparation method steps are as follows:

[0055] S1, smelting: raw materials are prepared according to the atomic percentage of the chemical composition of the high-entropy alloy, the raw materials are Mn electrolytic sheet, Cr electrolytic sheet, Fe electrolytic sheet, Co block and graphite with a purity of not less than 99.9%; the prepared raw materials are placed in a vacuum induction furnace for smelting, before smelting, first, in-furnace gas washing operation is performed: the furnace is vacuumized, and when the vacuum degree is less than 1×10 -5 , 99.9% pure argon is filled, when the pressure in the furnace reaches-0.5MPa, the gas filling is stopped, after standing for 15min, the second vacuum gas washing operation is performed, the process is repeated for 3 times, and after the gas washing is completed, vacuum smelting is performed; the smelting temperature is 1500℃, after sufficient melting for 10min, the temperature is lowered to 1450℃, and the ingot is poured, the smelting process is repeated for 5 times, and finally the high-entropy alloy ingot with a thickness of 20mm is poured;

[0056] S2, high temperature rolling: the high-entropy alloy ingot is placed in a high-temperature furnace, heated to 900℃, and kept for 10 min, and then 8 passes of rolling are performed, with a total reduction of 50%, to obtain a plate with a thickness of 10 mm;

[0057] S3, homogenization heat treatment: the high-entropy alloy plate after high-temperature rolling is subjected to homogenization heat treatment, the heat treatment temperature is 1200℃, and the treatment time is 2h, and then water quenching to room temperature;

[0058] S4, room temperature cold rolling: the plate after homogenization heat treatment is subjected to multi-pass cold rolling at room temperature, with a reduction of 1mm per pass, and a rolling speed of 0.4s -1 , and finally a plate with a thickness of 5mm is obtained; the total reduction is 50%;

[0059] S5, recrystallization annealing: the cold-rolled plate is subjected to recrystallization annealing heat treatment, the treatment temperature is 850℃, and the treatment time is 30min, and then water quenching to room temperature, to obtain the FeMnCoCrC high-entropy alloy.

[0060] Comparative Example Two

[0061] A CoCrFeMnNi high-entropy alloy, according to atomic percentage, the chemical composition of the high-entropy alloy is: Fe: 20%, Mn: 20%, Co: 20%, Cr: 20%, Ni: 20%.

[0062] The high-entropy alloy of this comparative example is denoted as CoCrFeMnNi, and the preparation method steps are as follows:

[0063] S1, smelting: prepare raw materials according to the atomic percentage of the chemical composition of the high-entropy alloy, the raw materials are Mn electrolytic sheet, Cr electrolytic sheet, Fe electrolytic sheet, Co block and Nb block with a purity of not less than 99.9%; place the prepared raw materials in a vacuum induction furnace for smelting, first perform in-furnace gas washing operation before smelting: vacuumize the furnace, and when the vacuum degree is less than 1x10 -5 , stop filling when the pressure in the furnace reaches -0.5MPa, and after standing for 15min, perform the second vacuum gas washing operation, which is repeated for a total of 3 times, and after gas washing, vacuum smelting is performed; the smelting temperature is 1500℃, after fully melting for 10min, the temperature is lowered to 1450℃ for casting into an ingot, and the smelting process is repeated 5 times, finally casting into a high-entropy alloy ingot with a thickness of 20mm;

[0064] S2, high temperature rolling: the high-entropy alloy ingot is placed in a high-temperature furnace, heated to 900℃, and kept for 10 min, and then 8 passes of rolling are performed, with a total reduction of 50%, to obtain a plate with a thickness of 10 mm;

[0065] S3, homogenization heat treatment: the high-temperature rolled high-entropy alloy plate is subjected to homogenization heat treatment, the heat treatment temperature is 1200℃, the treatment time is 2h, and then water quenching to room temperature;

[0066] S4, room temperature cold rolling: the plate after homogenization heat treatment is subjected to multi-pass cold rolling at room temperature, the thickness of each pass is 1mm, and the rolling speed is 0.4s -1 , and finally a plate with a thickness of 5mm is obtained; the total thickness reduction is 50%;

[0067] S5, recrystallization annealing: the cold-rolled plate is subjected to recrystallization annealing heat treatment, the treatment temperature is 850℃, the treatment time is 30min, and then water quenching to room temperature, thereby obtaining a CoCrFeMnNi high-entropy alloy.

[0068] The high-entropy alloys of each example and comparative example are characterized by GB / T 15970.11-2022 Corrosion Stress Corrosion Test for Metals and Alloys Part 11: Guide for Hydrogen Embrittlement and Hydrogen Induced Cracking Test for Metals and Alloys. Figure 2 The tensile engineering stress-strain curves of the high-entropy alloy of Example 1 and the high-entropy alloys of Comparative Example 1 and Comparative Example 2 in a room-temperature non-hydrogen-filled air environment and under in-situ electrochemical hydrogen charging are compared. As can be seen from the figure, the Fe 49.45 Mn 30 Co 10 Cr 10 Nb 0.05 C 0.5 The room-temperature yield strength of the high-entropy alloy is 710MPa, the tensile strength is 1056MPa, and the elongation after fracture is 51%. The hydrogen embrittlement resistance is improved by 30% compared with the Fe 49.5 Mn 30 Co 10 Cr 10 C 0.5 high-entropy alloy, and by 15% compared with the CoCrFeMnNi high-entropy alloy. The yield strength is improved by 73% compared with the Fe 49.5 Mn 30 Co 10 Cr 10 C 0.5 high-entropy alloy, and by 136% compared with the CoCrFeMnNi high-entropy alloy.

[0069] The Fe 48.62 Mn 31 Co 10 Cr 10 Nb 0.08 C 0.3room temperature yield strength of 700 MPa, tensile strength of 1012 MPa, and elongation of 53%. The hydrogen embrittlement resistance is improved by 38% compared to the Fe 49.5 Mn 30 Co 10 Cr 10 C 0.5 room temperature yield strength of 695 MPa, tensile strength of 1118 MPa, and elongation of 54%. The hydrogen embrittlement resistance is improved by 69% compared to the Fe 49.5 Mn 30 Co 10 Cr 10 C 0.5 room temperature yield strength of 695 MPa, tensile strength of 1118 MPa, and elongation of 54%. The hydrogen embrittlement resistance is improved by 69% compared to the Fe

[0070] Figure 3 room temperature tensile stress-strain curves of the high-entropy alloy of Example Three and the high-entropy alloy of Comparative Example One in a non-hydrogen charged air environment at room temperature and in-situ electrochemical hydrogen charging. It can be seen from the figure that the Fe 49.4 Mn 30 Co 10 Cr 10 Nb 0.1 C 0.5 room temperature yield strength of 695 MPa, tensile strength of 1118 MPa, and elongation of 54%. The hydrogen embrittlement resistance is improved by 69% compared to the Fe 49.5 Mn 30 Co 10 Cr 10 C 0.5 room temperature yield strength of 695 MPa, tensile strength of 1118 MPa, and elongation of 54%. The hydrogen embrittlement resistance is improved by 69% compared to the Fe 49.5 Mn 30 Co 10 Cr 10 C 0.5 room temperature yield strength of 695 MPa, tensile strength of 1118 MPa, and elongation of 54%. The hydrogen embrittlement resistance is improved by 69% compared to the Fe

[0071] Example Four

[0072] A high-strength and high-toughness Nb micro-alloyed high-entropy alloy, according to atomic percentage, the chemical composition of the high-entropy alloy is: Fe: 49.72%, Mn: 28%, Co: 11%, Cr: 11%, C: 0.2%, Nb: 0.08%; the microstructure of the high-entropy alloy is composed of an austenitic matrix, and nanometer NbC precipitates are dispersedly distributed in the crystal and the grain boundary, and the phase interface between the NbC precipitates and the austenitic matrix is semi-coherent.

[0073] The preparation method of the high-strength and high-toughness Nb micro-alloyed high-entropy alloy of the present embodiment comprises the following steps:

[0074] S1, smelting: raw materials are prepared according to the atomic percentage of the chemical composition of the high-entropy alloy, the raw materials are Mn electrolytic sheet, Cr electrolytic sheet, Fe electrolytic sheet, Co block, Nb block and graphite with a purity of not less than 99.9%; the prepared raw materials are placed in a vacuum induction furnace for smelting, and before smelting, an in-furnace gas washing operation is performed: the furnace is evacuated, and when the vacuum degree is less than 1*10 -5 -5 MPa, argon with a purity of 99.9% is filled, and when the pressure in the furnace reaches-0.5 MPa, the gas filling is stopped, and after standing for 15 min, a second vacuum gas washing operation is performed, and the process is repeated for a total of 3 times, and after the gas washing is completed, vacuum smelting is performed; the smelting temperature is 1400℃, and after sufficient melting for 13 min, the temperature is lowered to 1350℃ for casting into an ingot, and the smelting process is repeated for 4 times, and finally an ingot with a thickness of 20 mm of the high-entropy alloy is cast;

[0075] S2, high-temperature rolling: the high-entropy alloy ingot is placed in a high-temperature furnace, heated to 1000℃, and kept for 8 min, and then rolled for 7 passes with a total reduction of 60% to obtain a plate with a thickness of 10 mm;

[0076] S3, homogenization heat treatment: the high-entropy alloy plate after high-temperature rolling is subjected to homogenization heat treatment, the heat treatment temperature is 1250℃, and the treatment time is 4 h, and then water quenching to room temperature;

[0077] S4, room temperature cold rolling: the plate after homogenization heat treatment is subjected to multi-pass cold rolling at room temperature, each pass is reduced by 0.8 mm, and the rolling speed is 0.5 s -1 , and finally a plate with a thickness of 5 mm is obtained; the total reduction is 50%;

[0078] S5, recrystallization annealing: the cold-rolled plate is subjected to recrystallization annealing heat treatment, the treatment temperature is 750℃, and the treatment time is 10 min, and then water quenching to room temperature, thereby obtaining the Nb micro-alloyed high-entropy alloy with high strength and toughness and hydrogen embrittlement resistance.

[0079] Example five

[0080] A Nb micro-alloyed high-entropy alloy with high strength and toughness and hydrogen embrittlement resistance, according to atomic percentage, the chemical composition of the high-entropy alloy is: Fe: 48.32%, Mn: 33%, Co: 9%, Cr: 9%, C: 0.6%, Nb: 0.08%; the microstructure of the high-entropy alloy is composed of austenite matrix, and nanometer NbC precipitates are dispersedly distributed in the crystal and at the grain boundary, and the phase interface between the NbC precipitates and the austenite matrix is semi-coherent.

[0081] The preparation method of the Nb micro-alloyed high-entropy alloy with high strength and toughness and hydrogen embrittlement resistance in this example comprises the following steps:

[0082] S1, smelting: raw materials are prepared according to the atomic percentage of the chemical composition of the high-entropy alloy, the raw materials are Mn electrolytic sheet, Cr electrolytic sheet, Fe electrolytic sheet, Co block, Nb block and graphite with a purity of not less than 99.9%; the prepared raw materials are placed in a vacuum induction furnace for smelting, and before smelting, an in-furnace gas washing operation is performed: the furnace is evacuated, and when the vacuum degree is less than 1x10 -5 -5 Pa, 99.9% pure argon is filled, when the pressure in the furnace reaches-0.5 MPa, the gas filling is stopped, after standing for 15 min, a second vacuum gas washing operation is performed, the process is repeated for a total of 3 times, and after the gas washing is completed, vacuum smelting is performed; the smelting temperature is 1480℃, after sufficient melting for 15 min, the temperature is lowered to 1400℃ for casting into an ingot, the smelting process is repeated for 5 times, and finally a high-entropy alloy ingot with a thickness of 20 mm is cast;

[0083] S2, high-temperature rolling: the high-entropy alloy ingot is placed in a high-temperature furnace, heated to 950℃, and kept for 10 min, then 9 passes of rolling are performed, with a total reduction of 55%, to obtain a plate with a thickness of 10 mm;

[0084] S3, homogenization heat treatment: the high-entropy alloy plate after high-temperature rolling is subjected to homogenization heat treatment, the heat treatment temperature is 1230℃, and the treatment time is 3 h, then water quenching to room temperature;

[0085] S4, room temperature cold rolling: the plate after homogenization heat treatment is subjected to multi-pass cold rolling at room temperature, with a reduction of 0.8 mm per pass, and a rolling speed of 0.5s -1 , and finally a plate with a thickness of 5 mm is obtained; the total reduction is 50%;

[0086] S5, recrystallization annealing: the cold-rolled plate is subjected to recrystallization annealing heat treatment, the treatment temperature is 850℃, and the treatment time is 20 min, then water quenching to room temperature, thereby obtaining the high-strength and high-toughness Nb micro-alloyed high-entropy alloy with hydrogen embrittlement resistance.

Claims

1. A high-strength, high-toughness, hydrogen-embrittlement-resistant Nb microalloyed high-entropy alloy, characterized in that: The chemical composition of the Nb microalloyed high-entropy alloy, based on atomic percentage, is as follows: C: 0.2-0.6%, Nb: 0.05-0.1%, Mn: 28-33%, Co: 9-11%, Cr: 9-11%, with the balance being Fe and other unavoidable impurities. The microstructure of the high-entropy alloy consists of an austenitic matrix, with dispersed nano-NbC precipitates within the grains and at the grain boundaries. Furthermore, the NbC precipitates and the austenitic matrix exhibit a semi-coherent phase interface.

2. The high-strength, high-toughness, and hydrogen-embrittlement-resistant Nb microalloyed high-entropy alloy according to claim 1, characterized in that: The content of Mn is 30%, the content of Co is 10%, and the content of Cr is 10% by atomic percentage.

3. A high-strength, high-toughness, hydrogen-embrittlement-resistant Nb microalloyed high-entropy alloy according to any one of claims 1-2, characterized in that: The content of C is 0.3-0.5% by atomic percentage.

4. A method for preparing a high-strength, high-toughness, hydrogen-embrittlement-resistant Nb microalloyed high-entropy alloy as described in any one of claims 1-3, comprising the following steps: S1. Melting: Prepare raw materials according to the atomic percentage of the chemical composition of the high-entropy alloy. Place the prepared raw materials in a vacuum induction furnace for melting at a temperature of 1400-1500℃. After melting for 10-15 minutes, cool down to 1350-1450℃ and pour into an ingot. Repeat the melting process 4-5 times to finally pour into a high-entropy alloy ingot. S2. High-temperature rolling: The high-entropy alloy ingot is placed in a high-temperature furnace, heated to 900-1000℃, held for 8-12 minutes, and then rolled in multiple passes with a total reduction of 50-60% to obtain high-entropy alloy sheet. S3. Homogenization heat treatment: The high-entropy alloy sheet rolled at high temperature is subjected to homogenization heat treatment at a temperature of 1200-1250℃ for 2-4 hours, and then water quenched to room temperature. S4. Room temperature cold rolling: The high-entropy alloy sheet after homogenization heat treatment is subjected to multiple cold rolling processes at room temperature, with a total reduction of 50%. S5. Recrystallization Annealing: The cold-rolled high-entropy alloy sheet is subjected to recrystallization annealing heat treatment at a temperature of 750-900℃ for 10-30 minutes, and then water-quenched to room temperature to obtain a high-strength, high-toughness, and hydrogen-embrittlement-resistant Nb microalloyed high-entropy alloy.

5. The method for preparing a high-strength, high-toughness, hydrogen-embrittlement-resistant Nb microalloyed high-entropy alloy according to claim 4, characterized in that: Before placing the prepared raw materials in a vacuum induction furnace for melting in step S1, a furnace cleaning operation is performed, specifically including evacuating the furnace until the vacuum degree is less than 1×10⁻⁶. -5 Then, argon gas with a purity of 99.9% is introduced. When the pressure inside the furnace reaches -0.5MPa, the gas introduction is stopped. After standing for 15 minutes, a second vacuum purging operation is performed. This process is repeated 3 times.

6. The method for preparing a high-strength, high-toughness, hydrogen-embrittlement-resistant Nb microalloyed high-entropy alloy according to claim 4, characterized in that: In step S2, the high-temperature rolling process involves 7-9 rolling passes.

7. The method for preparing a high-strength, high-toughness, hydrogen-embrittlement-resistant Nb microalloyed high-entropy alloy according to claim 4, characterized in that: In step S4, room temperature cold rolling, 5-7 rolling passes are performed.

Images