A high-toughness fecrni-based dual-phase multi-principal-element alloy sheet and a preparation method thereof

Abstract

The application belongs to the technical field of alloy material preparation, and particularly discloses a high-strength and high-toughness FeCrNi series dual-phase multi-main-element alloy sheet and a preparation method thereof. 40 Cr 40 Ni 20 The high-strength and high-toughness FeCrNi series dual-phase multi-main-element alloy sheet is composed of Fe, Cr and Ni in terms of atomic percentage 40 Cr 40 Ni 20 The alloy is prepared by a vacuum arc furnace melting process, is subjected to homogenization annealing treatment and thermal mechanical treatment, has a dual-phase structure of BCC phase and FCC phase, has a tensile strength of 1180 MPa, and has an elongation of 13%. The preparation method is convenient to operate, easy to control, stable in effect, widely applicable, and strong in universality, and the prepared alloy has high strength and high toughness, and is expected to be applied in harsh working conditions such as aerospace, ocean, automobile and petrochemical industry.

Description

Technical Field

[0001] This invention relates to the field of alloy material preparation technology, and in particular to a high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheet and its preparation method. Background Technology

[0002] Metallic materials have played a vital role throughout human history, boasting the longest period of systematic research and application, and remaining one of the most widely used materials today. Metallic materials possess advantages such as high elastic modulus, high toughness, and high strength and hardness. Furthermore, their wide variety, diverse types, and relatively mature processing technologies contribute to their crucial position in the field of materials science. With societal progress and scientific development, materials with high strength, high toughness, high corrosion resistance, and good processing performance are the main development direction for engineering structural materials, with broad application prospects in aerospace, marine, automotive, and petroleum fields. To explore new directions and break through traditional design concepts, researchers have begun bold attempts and innovations in the design of multi-principal element alloys, attempting to develop new metallic materials with excellent comprehensive performance. This has led to the emergence of high-entropy alloys (multi-principal element alloys), opening a new world for exploring a vast field of alloy composition.

[0003] Multi-principal element alloys possess a unique combination of properties unattainable by traditional alloys, including high strength and hardness, excellent resistance to high-temperature softening, unique magnetic properties, superior corrosion and oxidation resistance, strong fatigue resistance, attractive tribological properties, good creep resistance, excellent radiation resistance at low temperatures, high thermal stability, and excellent mechanical properties. Furthermore, although containing multiple alloying elements, multi-principal element alloys can form a single solid solution structure, such as face-centered cubic (FCC) and body-centered cubic (BCC), allowing for customized mechanical behavior to achieve high strength, high hardness, wear resistance, corrosion resistance, and high-temperature resistance as needed. High-entropy alloys with a body-centered cubic structure exhibit high strength and low ductility at room temperature; while high-entropy alloys with a face-centered cubic structure possess excellent ductility but low strength at room temperature, typically requiring complex manufacturing processes to improve strength. Therefore, developing multi-principal element alloys with both face-centered cubic and body-centered cubic dual-phase structures holds promise for achieving a superior balance between strength and ductility. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a high-strength and tough FeCrNi-based dual-phase multi-principal-element alloy sheet and its preparation method.

[0005] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0006] The first objective of this invention is to provide a high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheet, wherein the high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheet is composed of Fe, Cr, and Ni elements in atomic percentage order. 40 Cr 40 Ni 20 .

[0007] The second objective of this invention is to provide a method for preparing high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheets, comprising the following steps:

[0008] S1, according to Fe 40 Cr 40 Ni 20 The atomic percentage of each element was measured from the pretreated Fe, Cr, and Ni elements.

[0009] S2. The alloy is smelted in a vacuum electric arc furnace.

[0010] S3. The smelted alloy is cooled to water-cooling temperature in a vacuum arc furnace and then taken out and subjected to homogenization annealing treatment.

[0011] S4. The alloy that has undergone homogenization annealing is processed into metal sheets with a thickness of 8.1-8.2 mm. Then, the surface of the metal sheet is polished with 120#-600# sandpaper to remove the oxide layer and impurities, so that the final metal sheet thickness is 8 mm. Finally, the metal sheet is subjected to thermomechanical treatment.

[0012] 1) Cold deformation treatment:

[0013] An 8mm thick metal sheet is cold rolled at room temperature with a total reduction of 80% ± 2%. Multiple small reductions are used, with each reduction not exceeding 10%, resulting in a final thickness of 1.6mm.

[0014] 2) Heat treatment:

[0015] The cold-rolled metal sheet is placed in a box-type muffle furnace and held at 900℃±5℃ for 3min±0.2min. Then the metal sheet is taken out and water-quenched to room temperature to obtain a high-strength and tough FeCrNi dual-phase multi-principal-element alloy sheet.

[0016] Furthermore, in step S1, the purity of Fe, Cr, and Ni elements is greater than 99.9%, and the pretreatment specifically includes:

[0017] S11. First, grind off the oxide scale on the surface of Fe, Cr, and Ni elements;

[0018] S12. Place the polished Fe, Cr, and Ni elements into a beaker containing anhydrous ethanol, and then place them together in an ultrasonic cleaner for 10-15 minutes to remove impurities and oil stains from the metal surface. Finally, remove the Fe, Cr, and Ni elements and air dry them.

[0019] Furthermore, the specific smelting process in step S2 is as follows:

[0020] S21. Place the Ni, Fe, and Cr elements sequentially into one of the copper crucibles in the water-cooled copper mold melting pool of the vacuum electric arc furnace, and then place the titanium ingots into the other copper crucible before closing the furnace.

[0021] S22. Evacuate the furnace to below 3.0E-3Pa;

[0022] S23. Fill with argon gas with a purity greater than 99.997% at a pressure of 0.05-0.06 MPa;

[0023] S24. First, melt the titanium ingot and observe whether it changes color after cooling. If it changes color, stop melting, check the sealing of the electric arc furnace, and re-vacuum it before replacing the titanium ingot and repeating the above operation. If it does not change color, start melting the alloy.

[0024] S25. The alloy is repeatedly melted 4 to 5 times. After each melting and cooling, the alloy is flipped over by a robotic arm for the next melting. In the third and subsequent meltings, the electromagnetic stirrer is turned on after the alloy melts to ensure that the ingot composition is uniform. After melting, the alloy is cooled to water-cooled temperature in a vacuum arc furnace and then removed.

[0025] Furthermore, in step S3, the homogenization annealing process specifically includes:

[0026] S31. Apply a high-temperature resistant coating to the alloy surface taken out of the vacuum arc furnace to reduce high-temperature oxidation loss on the alloy surface.

[0027] S32. Heat the muffle furnace to 1200℃±5℃, then put the alloy in and hold for 24 hours.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] 1. The FeCrNi-based duplex multi-principal element alloy sheet prepared by this invention exhibits significantly superior strength and corrosion resistance compared to existing commercially available super duplex stainless steels (such as SAF2507). Its room temperature yield strength reaches 1180 MPa, and its tensile strength is 1257 MPa, far exceeding that of conventional commercially available super duplex stainless steels, while also maintaining an elongation of 13%. Furthermore, this alloy has a high Cr content (38%–42% atomic percentage), providing a certain degree of corrosion resistance.

[0030] 2. The FeCrNi-based dual-phase multi-principal-element alloy sheet obtained by this invention uses inexpensive alloying elements, and its raw material cost is close to that of stainless steel and far lower than that of titanium alloys and high-temperature alloys.

[0031] In summary, this invention proposes a novel FeCrNi-based dual-phase multi-principal-element alloy sheet based on Fe, Cr, and Ni, the three main elements commonly used in stainless steel. The nominal composition of this alloy is Fe... 40 Cr 40 Ni 20 (Atomic percentage) The alloy is prepared by vacuum electric arc furnace melting process and undergoes homogenization annealing and thermomechanical treatment. The resulting alloy has a dual-phase structure of BCC phase and FCC phase, with a tensile strength of up to 1180MPa and an elongation of 13%.

[0032] The preparation method used in this invention is convenient to operate, easy to control, has stable effects, wide applicability, and strong versatility. The prepared alloy has high strength and high toughness and is expected to be used in harsh working environments such as aerospace, marine, automotive, and petrochemical industries. Attached Figure Description

[0033] Figure 1 Fe for thermomechanical treatment 40 Cr 40 Ni 20 XRD patterns of multi-principal element alloys.

[0034] Figure 2 Fe for thermomechanical treatment 40 Cr 40 Ni 20 Electron scanning images of multi-principal element alloys.

[0035] Figure 3 Fe for thermomechanical treatment 40 Cr 40 Ni 20 EDS elemental analysis images of multi-principal element alloys.

[0036] Figure 4 Fe for thermomechanical treatment 40 Cr 40 Ni 20 Stress-strain curves of multi-principal element alloy sheets under tensile conditions. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0038] All raw materials and reagents used in the following examples were commercially available. The vacuum arc furnace for melting the alloy was equipped with the DHL400 high-vacuum arc melting and suction casting system manufactured by Shenyang Scientific Instruments Co., Ltd., Chinese Academy of Sciences. This system is a non-consumable furnace, mainly composed of an arc melting vacuum chamber, an arc gun, an arc melting power supply, a five-station water-cooled copper crucible, a tilting robot, a magnetic stirrer, a working gas path, a system evacuation system, a vacuum measurement and electrical control system, an installation platform, and other components, and is equipped with a set of standard molds.

[0039] Example 1

[0040] This embodiment provides a high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheet, composed of Fe, Cr, and Ni elements in atomic percentage order. 40 Cr 40 Ni 20 The specific preparation process is as follows;

[0041] 1. Selection and pretreatment of raw materials: Fe, Cr and Ni elements with a purity greater than 99.9% (mass fraction / %) were selected for batching. The proportions of Fe, Cr and Ni elements are shown in Table 1.

[0042] Table 1

[0043]

[0044] Before mixing the ingredients, the oxide scale on the metal surface must be removed by grinding. Place the ground raw materials into a beaker containing anhydrous ethanol and put them into an ultrasonic cleaner for 10-15 minutes to remove impurities and oil stains from the metal surface. Finally, remove the raw materials and let them air dry.

[0045] 2. Ingredient Calculation and Weighing: Determine the total mass of the raw materials required for preparation as 150g, then weigh according to the nominal alloy composition Fe. 40 Cr 40 Ni 20 The atomic percentage of each element was calculated, along with the required mass percentage and specific mass (rounded to two decimal places, in g), as shown in Table 1. Three weighings were performed using an electronic balance to ensure accuracy, and the difference between each weighing result and the calculated standard mass was required to be no greater than ±0.02 g.

[0046] 3. Melting Equipment Requirements and Specific Operations: Following the order of melting points of the elements in the alloy, from lowest to highest, place Ni, Fe, and Cr elements sequentially into one copper crucible in a water-cooled copper mold melting tank. Place the titanium ingot into another copper crucible and close the furnace. Turn on the mechanical pump and evacuate to below 3.0E0Pa. Turn on the solenoid valve and the molecular pump, evacuating to below 3.0E-3Pa. Once the target is reached, turn off the solenoid valve and the molecular pump sequentially. Introduce 0.05–0.06Pa of high-purity argon gas (purity greater than 99.997%). First, melt the titanium ingot and observe whether it changes color after cooling. If it changes color, stop melting, check the sealing of the electric arc furnace, and re-evacuate. Replace the titanium ingot and repeat the above operation. If it does not change color, the alloy can be melted. Repeat the melting process 4–5 times. After each melting and cooling, use a robotic arm to flip the ingot for the next melting. In each subsequent melting, after the alloy melts, turn on the electromagnetic stirrer to ensure uniform ingot composition. After melting, the material is cooled to water-cooled temperature in an electric arc furnace before being removed.

[0047] 4. Homogenization treatment of the alloy: Before homogenization treatment, a high-temperature resistant coating needs to be applied to the surface of the ingot to reduce the high-temperature oxidation loss of the alloy surface. First, heat the muffle furnace to 1200℃, then put the ingot in, and the homogenization annealing temperature is 1200℃ (±5℃) for 24 hours.

[0048] 5. Alloy Sample Preparation and Thermomechanical Treatment: First, the homogenized annealed ingot is machined into metal sheets of 8.1–8.2 mm using an EDM wire cutter. Then, the surface of the metal sheet is polished with low-magnification (120#–600#) sandpaper to remove the oxide layer and impurities, resulting in a final metal sheet thickness of 8 mm. Cold Deformation Treatment: The 8 mm thick metal sheet is cold rolled at room temperature with a total reduction of 78–82%, using multiple passes with small reductions, each reduction not exceeding 10%, to a thickness of 1.6 mm. The cold-rolled metal sheet is then placed in a box-type muffle furnace and held at that temperature for a period of time for heat treatment at 900℃ (±5℃) for 3 minutes (±0.2 min). Afterward, it is removed and water-quenched to room temperature to obtain a high-strength and tough FeCrNi-based dual-phase multi-principal element alloy sheet.

[0049] Example 2

[0050] The performance of the high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheet prepared in Example 1 was tested:

[0051] 1. Organizational Analysis:

[0052] The thermomechanically treated sample was cut into 10mm × 10mm × 1.6mm electron scanning samples using an EDM wire cutter. The sample was then polished with 600# to 3000# sandpaper. After mechanical polishing, electrochemical polishing was performed at room temperature using a polishing solution of 90mL H2ClO4 + 10mL C2H5OH (100mL), an etching voltage of 30V, and a time of 20–30s. Following electrochemical polishing, the sample was etched with aqua regia using a etching solution of 60mL HCl + 20mL HNO3 (80mL), for 10–15s. The crystal structure of the sample was characterized using a D / max2200PC X-ray diffractometer (XRD, CuKα) with a scanning angle of 20°–100° and a scanning rate of 10° / min. The microstructure and chemical composition of the sample were analyzed using a JSM-IT800 field emission scanning electron microscope and energy dispersive spectroscopy.

[0053] Figure 1 Fe treated with thermomechanical methods in Example 1 40 Cr 40 Ni 20 XRD patterns of multi-principal element alloys, from Figure 1 It can be seen from this that the alloy has a dual-phase structure of FCC and BCC;

[0054] Figure 2 Fe treated with thermomechanical methods in Example 1 40 Cr 40 Ni 20 Electron scanning images of multi-principal element alloys, by Figure 2 It can be seen that the thermomechanical treatment of Fe 40 Cr 40 Ni 20 The microstructure of the multi-principal element alloy consists of black and white regions. The black regions have relatively smooth surfaces and contain pits from detached particles, while the white regions have irregular, uneven surfaces and are composed of clusters, thin strips, and long strips.

[0055] Figure 3 Fe treated with thermomechanical methods in Example 1 40 Cr 40 Ni 20 EDS elemental analysis images of multi-principal element alloys. (Source: [Insert Source Here]) Figure 3 It can be seen that the black areas of the alloy are rich in Ni, while Cr is concentrated in the white areas.

[0056] 2. Mechanical property testing:

[0057] Two standard dog bone tensile specimens were cut from the mechanically processed specimen of Example 1 using an electrical discharge wire cutter. The equipment used was a Bairoe-5 KN (video extensometer) mechanical testing machine. The tensile strain rate was 0.6 mm / min. Before the test, the standard tensile test gauge length was polished smooth and free of scratches. Then, the width and thickness of the gauge length of the specimen were measured using a micrometer, and the average value was taken for three measurements. During the test, the lower end of the specimen was clamped first to keep it straight. After opening the specimen protection, the upper end was clamped, and then the value was zeroed. The width and thickness of the gauge length of the tensile specimen were entered before the test began. The value was zeroed before each test. The tensile data were obtained. If the three results were not significantly different, the tensile stress-strain curve of the alloy sheet was plotted using Origin software.

[0058] Figure 4 It is a thermomechanically treated Fe 40 Cr 40 Ni 20 The tensile stress-strain curve of a multi-principal element alloy sheet is shown in the figure. Figure 4 It can be seen that the yield strength of the alloy sheet is about 1180 MPa, the fracture strength is about 1257 MPa, and the elongation is about 13%.

[0059] In summary, the high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheet prepared by this invention... 40 Cr 40 Ni 20 It has a two-phase structure with BCC and FCC phases, high tensile strength, and good elongation.

[0060] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheet, characterized in that, Includes the following steps: S1, according to Fe 40 Cr 40 Ni 20 The atomic percentage of each element was measured from the pretreated Fe, Cr, and Ni elements. S2. The alloy is smelted in a vacuum electric arc furnace. S3. The smelted alloy is cooled to water-cooling temperature in a vacuum arc furnace and then taken out and subjected to homogenization annealing treatment. S4. The alloy that has undergone homogenization annealing is processed into metal sheets with a thickness of 8.1-8.2 mm. Then, the surface of the metal sheet is polished with 120#-600# sandpaper to remove the oxide layer and impurities, so that the final metal sheet thickness is 8 mm. Finally, the metal sheet is subjected to thermomechanical treatment. 1) Cold deformation treatment: An 8mm thick metal sheet is cold rolled at room temperature with a total reduction of 80% ± 2%. Multiple small reductions are used, with each reduction not exceeding 10%, resulting in a final thickness of 1.6mm. 2) Heat treatment: Cold-rolled metal sheets are placed in a box-type muffle furnace and held at 900℃±5℃ for 3min±0.2min. The sheets are then removed and water-quenched to room temperature to obtain high-strength, high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheets. 40 Cr 40 Ni 20 .

2. The method for preparing high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheets according to claim 1, characterized in that, In step S1, the purity of Fe, Cr, and Ni elements is greater than 99.9%, and the pretreatment specifically includes: S11. First, grind off the oxide scale on the surface of Fe, Cr, and Ni elements; S12. Place the polished Fe, Cr, and Ni elements into a beaker containing anhydrous ethanol, and then place them together in an ultrasonic cleaner for 10-15 minutes to remove impurities and oil stains from the metal surface. Finally, remove the Fe, Cr, and Ni elements and air dry them.

3. The method for preparing high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheets according to claim 1, characterized in that, The specific smelting process in step S2 is as follows: S21. Ni, Fe, and Cr elements are placed sequentially into one copper crucible in the water-cooled copper mold melting pool of the vacuum electric arc furnace, and titanium ingots are placed into another copper crucible before the furnace is closed. S22. Evacuate the furnace to below 3.0E-3Pa; S23. Fill with argon gas with a purity greater than 99.997% at a pressure of 0.05–0.06 MPa; S24. First, melt the titanium ingot and observe whether it changes color after cooling. If it changes color, stop melting, check the sealing of the electric arc furnace, and re-vacuum it before replacing the titanium ingot and repeating the above operation. If it does not change color, start melting the alloy. S25. Repeat the alloy melting process 4 to 5 times. After each melting and cooling, use a robotic arm to flip the alloy over for the next melting. In the third and subsequent melting processes, turn on the electromagnetic stirrer after the alloy melts to ensure uniform composition of the ingot. After melting, cool the ingot to water-cooling temperature in a vacuum arc furnace before removing it from the furnace.

4. The method for preparing high-strength and high-toughness FeCrNi-based dual-phase multi-principal-element alloy sheets according to claim 1, characterized in that, In step S3, the homogenization annealing process specifically includes: S31. Apply a high-temperature resistant coating to the surface of the alloy taken out of the vacuum arc furnace to reduce the high-temperature oxidation loss of the alloy surface. S32. Heat the muffle furnace to 1200℃±5℃, then put the alloy in and hold for 24 hours.

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