A high-strength (CoCrNi) 94-x Al3Ti3Nb x Multi-principal element alloys and their preparation methods

Abstract

Embodiments of the present application disclose a high-strength (CoCrNi) 94‑x Al3Ti3Nb x Multi-principal element alloy and preparation method thereof, relate to the technical field of alloy materials, and aim to solve the current situation that the existing homogeneous structure single-phase CoCrNi multi-principal element alloy has low strength and is difficult to meet the demand of high-end service environment. The present application aims to improve the mechanical properties of the CoCrNi-based alloy through microstructure regulation and composition design, so as to expand the applicability of the CoCrNi-based alloy in more severe application fields. The preparation method comprises the following steps: vacuum arc melting treatment is performed on a plurality of metal elemental raw materials to obtain an alloy ingot; the metal elemental raw materials comprise Co, Cr, Ni, Al, Ti and Nb; cold rolling treatment is performed on the alloy ingot to obtain an alloy plate; the alloy plate is sequentially subjected to solid solution treatment, annealing treatment and aging treatment to obtain a (CoCrNi) 94‑ x Al3Ti3Nb x Multi-principal element alloy.

Description

Technical Field

[0001] This application relates to the field of alloy materials technology, specifically to a high-strength (CoCrNi) alloy. 94-x Al3Ti3Nb x Multi-principal element alloys and their preparation methods. Background Technology

[0002] Modern engineering has an urgent need for alloys that combine high strength and good ductility. Single-phase homogeneous CoCrNi multi-principal-element alloys have become a research hotspot due to their stable FCC structure and excellent mechanical properties. However, their room temperature yield strength is still relatively low, which limits their engineering applications.

[0003] Employing a strategy of controlling non-uniform microstructures and nano-precipitates can effectively improve the strength-ductility matching properties of materials. During plastic deformation, non-uniform structures can induce the accumulation of geometrically necessary dislocations, thereby generating non-uniform deformation-induced work hardening. Meanwhile, coherent / tough nano-precipitates can effectively interact with dislocations during deformation, alleviating stress concentration effects and contributing to strengthening and hardening. However, during heat treatment, micron-sized non-coherent / hard precipitates easily form within the alloy. These precipitates often aggregate at grain boundaries, leading to strain concentration regions during plastic deformation, which in turn induces cracks and reduces the material's strength and work hardening capacity. Microalloying technology can suppress the precipitation of brittle phases at grain boundaries, a technique already validated in traditional alloys. This design strategy has also been introduced into some multi-principal alloy systems. For example, adding trace amounts of Al, Ti, and Nb to NiCoFeCr-based multi-principal alloys can introduce Ni3(Al,Ti) type L12 precipitates into the grains, effectively enhancing work hardening ability and plastic stability. At the same time, Nb elements preferentially distribute to the coherent L12 precipitates inside the grains during heat treatment, reducing the overall diffusion kinetics and enhancing the thermal stability of the L12 precipitates, thereby effectively suppressing the formation of brittle phases at grain boundaries. Summary of the Invention

[0004] The main objective of this application is to provide a high-strength (CoCrNi) material. 94-x Al3Ti3Nb x The invention relates to multi-principal element alloys and their preparation methods, aiming to solve the technical problem that the performance of existing CoCrNi-based multi-principal element alloys is insufficient to meet application requirements.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows: In one aspect, embodiments of this application provide a high-strength (CoCrNi) material. 94-x Al3Ti3Nb x The preparation method of multi-principal element alloys includes the following steps: A variety of elemental metals are subjected to vacuum arc melting to obtain alloy ingots; the elemental metals include Co, Cr, Ni, Al, Ti and Nb. The alloy ingot is cold-rolled to obtain alloy sheet; The alloy sheet was subjected to solution treatment, annealing treatment and aging treatment in sequence to obtain (CoCrNi). 94- x Al3Ti3Nb x Multi-principal element alloy, 1≤x≤3.

[0006] As some optional embodiments of this application, the step of performing vacuum arc melting on multiple elemental metal raw materials to obtain alloy ingots includes: The various metal elemental raw materials are placed in a vacuum arc melting furnace for vacuum arc melting treatment; wherein Al is placed at the bottom, Co, Ni and Ti are placed in the middle, and Nb and Cr are placed at the top.

[0007] As some optional embodiments of this application, the vacuum arc melting process includes: Close the melting chamber and evacuate to a vacuum level of 5 × 10⁻⁻⁵. 5 Below Pa, argon gas is introduced to -0.05 MPa, and the process of evacuation and argon gas introduction is repeated three times; Set the current to 380 A-400 A, melt Ti for 60 seconds and turn it over, repeating this process three times to remove residual oxygen in the furnace. Then, melt the elemental metals Co, Cr, Ni, Al, Ti, and Nb according to a preset ratio for 60-180 seconds, turning and melting five times to ensure the metal block is completely melted. After melting, pour the alloy melt into a copper mold and cool it to room temperature with the furnace before taking a sample.

[0008] As some optional embodiments of this application, before cold rolling the alloy ingot to obtain the alloy sheet, the method further includes: The alloy ingot was subjected to solution heat treatment at 1200 °C and held at this temperature for 2 hours, and then quenched in water to cool to room temperature.

[0009] As some optional embodiments of this application, the total reduction of the cold rolling process is 80%-90%.

[0010] As some optional embodiments of this application, the annealing treatment is performed at a temperature of 900℃-1050℃ and for a time of 60 min-240 min.

[0011] As some optional embodiments of this application, the aging treatment is carried out at a temperature of 600℃-800℃ and for a time of 10 min-240 min.

[0012] Secondly, embodiments of this application also provide a high-strength (CoCrNi) material. 94-x Al3Ti3Nb x Multi-principal element alloys are prepared by the method described above.

[0013] As some optional embodiments of this application, the high-strength (CoCrNi) 94-x Al3Ti3Nb x The multi-principal element alloy is composed of a stack of fully recrystallized CG regions (coarse grains) and incompletely recrystallized FG regions (fine grains), and also contains a large number of annealed twins. The average grain size of the CG region is about 13.06 μm, and the average grain size of the FG region is about 2.67 μm.

[0014] As some optional embodiments of this application, the high-strength (CoCrNi) 94-x Al3Ti3Nb x The tensile yield strength of the multi-principal element alloy is 1112 MPa-1770 MPa; the tensile ultimate strength is 1244 MPa-1818 MPa; and the uniform elongation is 1.12%-17.30%.

[0015] Compared with the prior art, the beneficial effects of this application are as follows: The technical solution of this application includes: vacuum arc melting of various elemental metal raw materials to obtain alloy ingots; the elemental metal raw materials include Co, Cr, Ni, Al, Ti and Nb; cold rolling of the alloy ingots to obtain alloy plates; and sequentially heat-treating, annealing and aging treatment of the alloy plates to obtain (CoCrNi). 94-x Al3Ti3Nb x This application describes a multi-principal element alloy. By controlling the amount of Nb added, brittle precipitates are avoided at grain boundaries. Simultaneously, the non-uniform grain structure is effectively preserved by adjusting the annealing temperature. This effectively prevents early fracture during plastic deformation. Furthermore, the use of annealing and aging heat treatment creates a dual heterogeneous structure within the alloy, encompassing both grain size and precipitates, resulting in non-uniform induced deformation strengthening and hardening, thus achieving a good balance between material strength and ductility. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the technical route involved in the embodiments of this application; Figure 2 The (CoCrNi) involved in the embodiments of this application. 94-x Al3Ti3Nbx XRD patterns of multi-principal element alloys; Figure 3 The (CoCrNi) involved in the embodiments of this application. 94-x Al3Ti3Nb x EBSD-inverse pole figure, grain boundary distribution map and grain size statistics of multi-principal element alloys; Figure 4 The (CoCrNi) involved in the embodiments of this application. 94-x Al3Ti3Nb x Energy spectrum of multi-principal element alloys; Figure 5 The (CoCrNi) involved in the embodiments of this application. 94-x Al3Ti3Nb x Stress-strain curves of room temperature tensile engineering of multi-principal element alloys; Figure 6 The (CoCrNi) involved in the embodiments of this application. 94-x Al3Ti3Nb x SEM images of fracture surfaces of multi-principal element alloys; Figure 7 The canine bone type (CoCrNi) involved in the embodiments of this application. 94-x Al3Ti3Nb x Multi-principal element alloy specimens. Detailed Implementation

[0017] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0018] In modern engineering, the development of alloy materials that combine high strength and good ductility is an urgent need; however, achieving this goal faces significant challenges. CoCrNi-based multi-principal alloys, with their stable face-centered cubic (FCC) structure and excellent mechanical properties, have become a research hotspot. Nevertheless, the relatively low yield strength of single-phase CoCrNi multi-principal alloys at room temperature limits their widespread application in engineering.

[0019] Studies have shown that constructing heterostructures and introducing nanoprecipitates can significantly improve the tensile yield strength and ductility of materials. Further research indicates that introducing trace amounts of Al and Ti elements into a CoCrNi matrix can induce coherent nanoprecipitates through both continuous and discontinuous precipitation. Continuous precipitation induces the formation of coherent nanoprecipitates within the grains, while discontinuous precipitation leads to the formation of micron-sized brittle precipitates at grain boundaries. These nanoprecipitates not only induce work hardening but also effectively suppress premature instability during plastic deformation. However, micron-sized precipitates typically aggregate near grain boundaries, providing potential sites for localized deformation and thus increasing the material's brittleness.

[0020] Microalloying technology has been proven to be an effective means of suppressing the precipitation of brittle phases at grain boundaries. Its mechanism of action is mainly manifested in regulating the thermodynamic properties of precipitation or changing the precipitation kinetics. This phenomenon has been fully verified in traditional alloy systems containing one or two principal components. However, research on the microalloying behavior in multi-principal alloys is still limited, especially for L12-strengthened multi-principal alloys. Further in-depth research is urgently needed to improve the technology system and obtain better strength and toughness.

[0021] Researchers have discovered that by adding 2 at.% Ti and 4 at.% Al to a FeCoNiCr matrix, combined with cold rolling and aging processes, the formation of nanoscale L12-Ni3(Ti,Al) coherent precipitates was successfully induced. This approach increased the alloy's yield strength to 1005 MPa and tensile strength to 1273 MPa, while maintaining an elongation of 17.00%. However, the precipitation strengthening contribution was only 327 MPa. This is because the L21 precipitate with a Ni2AlTi structure exists at the grain boundaries of this system. This type of precipitate is hard and brittle at room temperature, causing premature strain localization and limiting the full extent of the precipitation strengthening effect. Other researchers have found that adding 4 at.% Al, 4 at.% Ti, and different amounts of Mo to FeNiCrMn-based multi-principal alloys can yield L12-strengthened multi-principal alloys through cold rolling and heat treatment. When the Mo content is 1 at.%, it exhibits a yield strength of 720 MPa and a uniform elongation of 21.60%. However, as the Mo content increases to 5 at.%, the elongation drops sharply to 2.50%. The poor elongation is attributed to the formation of a Mo-rich σ phase at the initial defects of the alloy. The accumulation of a large number of dislocations at the σ phase / matrix interface causes local stress concentration, which in turn triggers brittle fracture that propagates along the interface.

[0022] Therefore, traditional microalloying elements tend to aggregate at interfaces or grain boundaries, generating brittle, incoherent precipitates at high-energy defects. During deformation and damage, stress concentration zones easily form near the interface, which can further develop into microcracks, initiating ductile instability in the early deformation process. This instability leads to a significant decrease in strength, weakens the non-uniform deformation-induced strengthening ability of the material, and consequently reduces the overall strength and work hardening capacity.

[0023] In view of this, this application introduces the microalloying element Nb to generate L12 nano-precipitates inside the grains while avoiding the generation of brittle precipitates at grain boundaries, thereby preventing early plastic instability during plastic deformation and ultimately obtaining a multi-principal element alloy with a good strength-plasticity synergy.

[0024] Specifically, a high-strength (CoCrNi) 94-x Al3Ti3Nb x Preparation methods of multi-principal element alloys, such as Figure 1 As shown, it includes the following steps: Step S10: Vacuum arc melting is performed on various elemental metal raw materials to obtain alloy ingots; the elemental metal raw materials include Co, Cr, Ni, Al, Ti and Nb.

[0025] More specifically, the process of vacuum arc melting multiple elemental metal raw materials to obtain alloy ingots includes: placing the multiple elemental metal raw materials into a vacuum arc melting furnace for vacuum arc melting; wherein Al is placed at the bottom, Co, Ni and Ti are placed in the middle, and Nb and Cr are placed at the top.

[0026] More specifically, the vacuum arc melting process includes: closing the melting chamber, evacuating to below 5×10-5 Pa, introducing argon gas to -0.05 MPa, and repeating the evacuation and argon gas introduction process three times; setting the current to 380 A-400 A, melting Ti for 60 s and then turning it over, repeating this process three times to remove residual oxygen in the melting furnace, and then melting the elemental metals Co, Cr, Ni, Al, Ti, and Nb according to a preset ratio for 60 s-180 s, and repeatedly turning and melting five times to ensure that the metal block is completely melted; after the melting is completed, casting the alloy melt into a copper mold, cooling it to room temperature with the furnace, and then taking a sample.

[0027] It should be noted that the purpose of the repeated vacuuming is to minimize the partial pressure of harmful gases in the smelting environment, thereby preventing contamination of the molten metal and promoting the removal of impurities. A single vacuuming operation can only remove free gases within the furnace cavity and cannot effectively remove gases adsorbed on the furnace walls and sample surfaces. Furthermore, each vacuuming operation reduces the vacuum level to 5 × 10⁻⁵ Pa, and each introduction of argon gas reduces the vacuum level to -0.05 MPa.

[0028] It should be noted that there are many crucibles inside the smelting furnace. One crucible holds the sample raw material to be smelted, and another crucible holds additional Ti particles specifically for absorbing residual oxygen.

[0029] More specifically, in the vacuum arc melting furnace apparatus, the furnace body is a sealed container. After the metal raw material is placed in, an inert gas is introduced. After the electrodes introduced from the top of the furnace and the water-cooled crystallizer at the bottom of the furnace are energized and an arc is generated, the heat of the arc melts the raw material and solidifies it in the crystallizer to obtain a metal ingot.

[0030] Step S20: The alloy ingot is cold-rolled to obtain alloy sheet.

[0031] More specifically, before cold rolling the alloy ingot to obtain the alloy sheet, the process further includes: subjecting the alloy ingot to solution heat treatment at 1200 °C, holding it at this temperature for 2 h, and then quenching it in water to cool it to room temperature.

[0032] The total reduction in the cold rolling process is 80%-90%. The cold rolling process involves extruding the smelted metal ingot into a sheet through rolling, which refines the grains and effectively improves the strength of the material.

[0033] Step S30: The alloy sheet is subjected to heat treatment, annealing treatment and aging treatment in sequence to obtain (CoCrNi). 94-x Al3Ti3Nb x Multi-principal element alloy, 1≤x≤3.

[0034] More specifically, the annealing treatment temperature is 900 ℃-1050 ℃, preferably 1000 ℃, and the treatment time is 60 min-240 min. The annealing treatment uses an existing tube furnace. During use, the obtained ingot is placed in it, and the composition inside the ingot is uniformly distributed through high-temperature solution treatment. It is then quenched in water to maintain the microstructure after solution treatment; that is, recrystallization annealing causes some of the fine grains after cold rolling to grow and form a heterogeneous structure.

[0035] More specifically, the aging treatment is carried out at a temperature of 600 ℃-800 ℃ for a time of 10 min-240 min. The aging treatment also employs an existing tube furnace, where L12 precipitates are generated inside the sample through aging heat treatment, thereby enhancing the strength of the material through precipitation strengthening.

[0036] To obtain high strength (CoCrNi) 94-x Al3Ti3Nb x In some preferred embodiments, after step S30, the multi-principal element alloy further includes: Step S40: For the (CoCrNi) 94-x Al3Ti3Nb x Multi-principal element alloys were subjected to XRD, EBSD, and EDS tests, and based on the test results, high-strength (CoCrNi) alloys were obtained. 94-x Al3Ti3Nb x Multi-principal element alloys.

[0037] More specifically, the (CoCrNi) 94-x Al3Ti3Nb x Multi-principal alloys were cut into dog-bone shaped specimens using wire electrical discharge machining (e.g.) Figure 7 As shown), the gauge length is 10mm, the width is 3mm, and the thickness is 1mm. After smoothing the surface and sides with 400#, 800#, 1500#, and 2000# sandpaper respectively, the mechanical properties of the multi-principal element alloy were tested using a universal testing machine. The tensile rate during the test was 1×10⁻⁶. -3 / s, the strain of the alloy was measured using DIC; the sample was cut into small pieces by wire EDM, and the surface was polished smooth with 400#, 800#, 1500# and 2000# sandpaper in sequence before being heat-mounted, mechanically polished with 3μm and 1μm diamond polishing fluid in sequence, and finally polished with 0.05μm silica suspension. After ultrasonic cleaning with anhydrous ethanol and drying, XRD, EBSD and EDS tests were performed.

[0038] A continuously moving fine metal wire was used as an electrode to induce pulsed spark discharge on a metal workpiece, which was then cut into dog-bone shaped specimens for tensile testing. The metal surface was then finely polished sequentially using polishing slurries of different particle sizes to obtain a clean, scratch-free specimen surface for subsequent characterization tests. The phase composition of the polished metal surface was obtained by scanning it with an X-ray diffractometer. The microstructure of the polished metal surface was obtained by imaging with a scanning electron microscope; the elemental distribution and grain orientation distribution were obtained using energy dispersive spectroscopy and electron backscatter diffraction. The dog-bone shaped specimen was fixed at both ends using a fixture, a load was applied, and the changes in load and displacement were recorded. The data were processed to obtain the quasi-static mechanical properties of the sample.

[0039] High-strength (CoCrNi) prepared using the above method 94-x Al3Ti3Nb x The multi-principal-element alloy consists of a stack of fully recrystallized CG regions and incompletely recrystallized FG regions, and also contains a large number of annealed twins. The average grain size of the CG region is about 13.06 μm, and the average grain size of the FG region is about 2.67 μm.

[0040] Tests have shown that the high-strength (CoCrNi) 94-x Al3Ti3Nb x The tensile yield strength of the multi-principal element alloy is 1112MPa-1770MPa; the tensile ultimate strength is 1244MPa-1818MPa; and the uniform elongation is 1.12%-17.30%.

[0041] The above method and alloy will be described in detail below with reference to specific embodiments: Example 1: (1) Co, Cr, Ni, Al, Ti, and Nb elemental metal raw materials were ultrasonically cleaned with alcohol and then vacuum dried. (CoCrNi) 93 Convert the atomic percentage of Al3Ti3Nb1 to the mass percentage and weigh the required metal raw materials. Place the metal raw materials in a vacuum arc melting furnace, placing the Al metal block at the bottom of the crucible, the Co, Ni, and Ti metal blocks in the middle, and the Nb and Cr elements on top. Close the melting chamber and evacuate to 5 × 10⁻⁶. -5 The pressure was lower than Pa, then argon gas was introduced to -0.05 MPa, and the vacuuming and argon gas introduction process was repeated three times. The current was set to 390 A, and the Ti ingot was melted for 60 s. The Ti ingot was turned over, and this process was repeated three times to remove residual oxygen in the melting furnace, and then (CoCrNi) was melted. 93 The Al3Ti3Nb1 multi-principal element alloy was melted for 60 seconds, and repeatedly turned over five times to ensure that the metal block was completely melted. After the melting was completed, the alloy melt was poured into a copper mold, cooled to room temperature in the furnace, and then sampled to obtain (CoCrNi).93 Al3Ti3Nb1 multi-principal-element alloy ingot.

[0042] (2) (CoCrNi) 93 Al3Ti3Nb1 multi-principal alloy ingots were subjected to solution heat treatment at 1200 ℃, held at this temperature for 2 h, and then quenched and cooled in water.

[0043] (3) Take the (CoCrNi) obtained in step (2) 93 Al3Ti3Nb1 multi-principal alloy ingots were cold-rolled to obtain rolled samples. The initial thickness of the ingots was 10 mm, the single rolling pressure was 0.2 mm, and the deformation was 90%.

[0044] (4) Take the (CoCrNi) obtained in step (3) 93 Al3Ti3Nb1 multi-principal element alloy sheets were annealed at 1000 ℃ for 1 h, then quenched in water, and then aged at 700 ℃ for 1 h, followed by quenching in water to obtain (CoCrNi). 93 Al3Ti3Nb1 multi-principal element alloy. The obtained multi-principal element alloy has a tensile yield strength of 1112 MPa, a tensile ultimate strength of 1443 MPa, and a uniform elongation of approximately 17.30% at room temperature.

[0045] Example 2: (1) Co, Cr, Ni, Al, Ti, and Nb elemental metal raw materials were ultrasonically cleaned with alcohol and then vacuum dried. (CoCrNi) 93 Convert the atomic percentage of Al3Ti3Nb1 to the mass percentage and weigh the required metal raw materials. Place the metal raw materials in a vacuum arc melting furnace, placing the Al metal block at the bottom of the crucible, the Co, Ni, and Ti metal blocks in the middle, and the Nb and Cr elements at the top. Close the melting chamber and evacuate to 5 × 10⁻⁶. -5 The pressure was lower than Pa, then argon gas was introduced to -0.05 MPa. The vacuuming and argon gas introduction process was repeated three times. The current was set to 390 A, and the Ti ingot was melted for 60 s. The Ti ingot was turned over, and this process was repeated three times to remove residual oxygen in the melting furnace. Then (CoCrNi) was melted. 93 The Al3Ti3Nb1 multi-principal element alloy was melted for 60 seconds, and repeatedly turned over five times to ensure that the metal block was completely melted. After the melting was completed, the alloy melt was poured into a copper mold, cooled to room temperature in the furnace, and then sampled to obtain (CoCrNi). 93 Al3Ti3Nb1 multi-principal-element alloy ingot.

[0046] (2) (CoCrNi) 93Al3Ti3Nb1 multi-principal alloy ingots were subjected to solution heat treatment at 1200 ℃, held at this temperature for 2 h, and then quenched and cooled in water.

[0047] (3) Take the (CoCrNi) obtained in step (2) 93 Al3Ti3Nb1 multi-principal alloy ingots were cold rolled and deformed. The initial thickness of the ingot was 10 mm, the single pressing amount was 0.2 mm, and the deformation amount was 90%.

[0048] (4) Take the (CoCrNi) obtained in step (3) 93 Al3Ti3Nb1 multi-principal element alloy sheet was annealed at 1000 ℃ for 1 h, then quenched in water, and then aged at 800 ℃ for 1 h, followed by quenching in water to obtain (CoCrNi). 93 Al3Ti3Nb1 multi-principal element alloy. The obtained multi-principal element alloy has a tensile yield strength of 1169 MPa, a tensile ultimate strength of 1490 MPa, and a uniform elongation of approximately 12.10% at room temperature.

[0049] Example 3: (1) Co, Cr, Ni, Al, Ti, and Nb elemental metal raw materials were ultrasonically cleaned with alcohol and then vacuum dried. (CoCrNi) 91 Convert the atomic percentage of Al3Ti3Nb3 to mass percentage and weigh the required metal raw materials. Place the metal raw materials in a vacuum arc melting furnace, placing the Al metal block at the bottom of the crucible, the Co, Ni, and Ti metal blocks in the middle, and the Nb and Cr elements at the top. Close the melting chamber and evacuate to 5 × 10⁻⁶. -5 The pressure was lower than Pa, then argon gas was introduced to -0.05 MPa. The vacuuming and argon gas introduction process was repeated three times. The current was set to 390 A, and the Ti ingot was melted for 60 s. The Ti ingot was turned over, and this process was repeated three times to remove residual oxygen in the melting furnace. Then (CoCrNi) was melted. 91 Al3Ti3Nb3 multi-principal element alloy was melted for 60 seconds, repeatedly turned over five times to ensure complete melting of the metal block. After melting, the alloy melt was poured into a copper mold, cooled to room temperature in the furnace, and sampled to obtain (CoCrNi). 91 Al3Ti3Nb3 multi-principal-element alloy ingot.

[0050] (2) (CoCrNi) 91 Al3Ti3Nb3 multi-principal-element alloy ingots were subjected to solution heat treatment at 1200 ℃, held at this temperature for 2 h, and then quenched and cooled in water.

[0051] (3) Take the (CoCrNi) obtained in step (2) 91Al3Ti3Nb3 multi-principal alloy ingots were cold-rolled with an initial thickness of 10 mm, a single rolling pressure of 0.2 mm, and a deformation rate of 90%. The resulting multi-principal alloy exhibited a tensile yield strength of 1770 MPa, a tensile ultimate strength of 1818 MPa, and a uniform elongation of approximately 2.70% at room temperature.

[0052] Example 4: (1) Co, Cr, Ni, Al, Ti, and Nb elemental metal raw materials were ultrasonically cleaned with alcohol and then vacuum dried. (CoCrNi) 91 Convert the atomic percentage of Al3Ti3Nb3 to mass percentage and weigh the required metal raw materials. Place the metal raw materials in a vacuum arc melting furnace, placing the Al metal block at the bottom of the crucible, the Co, Ni, and Ti metal blocks in the middle, and the Nb and Cr elements at the top. Close the melting chamber and evacuate to 5 × 10⁻⁶. -5 The pressure was lower than Pa, then argon gas was introduced to -0.05 MPa. The vacuuming and argon gas introduction process was repeated three times. The current was set to 390 A, and the Ti ingot was melted for 60 s. The Ti ingot was turned over, and this process was repeated three times to remove residual oxygen in the melting furnace. Then (CoCrNi) was melted. 91 Al3Ti3Nb3 multi-principal element alloy was melted for 60 seconds, repeatedly turned over five times to ensure complete melting of the metal block. After melting, the alloy melt was poured into a copper mold, cooled to room temperature in the furnace, and sampled to obtain (CoCrNi). 91 Al3Ti3Nb3 multi-principal-element alloy ingot.

[0053] (2) (CoCrNi) 91 Al3Ti3Nb3 multi-principal-element alloy ingots were subjected to solution heat treatment at 1200 ℃, held at this temperature for 2 h, and then quenched and cooled in water.

[0054] (3) Take the (CoCrNi) obtained in step (2) 91 Al3Ti3Nb3 multi-principal alloy ingots were cold rolled and deformed. The initial thickness of the ingot was 10 mm, the single pressing amount was 0.2 mm, and the deformation amount was 90%.

[0055] (4) Take the (CoCrNi) obtained in step (3) 91 Al3Ti3Nb3 multi-principal element alloy sheets were annealed at 1000 ℃ for 1 h, then quenched in water, and then aged at 700 ℃ for 1 h, followed by quenching in water to obtain (CoCrNi). 91 Al3Ti3Nb3 multi-principal element alloy. The obtained multi-principal element alloy has a tensile yield strength of 1244 MPa and a tensile ultimate strength of 1244 MPa at room temperature, and a uniform elongation of approximately 1.12%.

[0056] Experimental Example 1: The (CoCrNi) obtained in Examples 1 and 2 93 XRD tests were performed on the Al3Ti3Nb1 multi-principal element alloy, and the test results are shown in the figure below. Figure 2 As shown, the cold-rolled alloys are all single-phase FCC structures. After annealing and aging heat treatment, the samples consist of FCC and L12 phases. The volume fraction of the L12 phase inside the sample was obtained by peak fitting, where: The (CoCrNi) obtained in Example 1 93 The volume fraction of the L12 phase in the Al3Ti3Nb1 multi-principal element alloy is 27.99% after aging heat treatment at 700℃ and 8.98% after heat treatment at 800℃. The (CoCrNi) obtained in Example 2 91 The volume fraction of the L12 phase in Al3Ti3Nb3 after aging heat treatment at 700 ℃ is 0.80%; (CoCrNi) 91 The Al3Ti3Nb3 multi-principal-element alloy exhibits the highest lattice mismatch between the matrix and the precipitated phases.

[0057] Experimental Example 2: The (CoCrNi) obtained in Example 1 93 The inverse pole figure, grain boundary distribution diagram, and grain size statistics of Al3Ti3Nb1 after annealing at 1000℃ / 1h and aging at 700℃ / 1h are shown below. Figure 3 As shown in the inverse pole figure and grain boundary distribution map, the interior of the surface sample consists of a stack of fully recrystallized CG regions and incompletely recrystallized FG regions, with a large number of annealed twins present. The average grain size of the CG region is approximately 13.06 μm, and the average grain size of the FG region is approximately 2.67 μm.

[0058] Experimental Example 3: The (CoCrNi) obtained in Example 1 93 The energy dispersive spectroscopy (EDS) of Al3Ti3Nb1 after annealing at 1000 ℃ / 1 h and aging at 700 ℃ / 1 h is shown below. Figure 4 As shown in the figure, it can be seen that the various elements inside the sample are evenly distributed without obvious segregation.

[0059] Experimental Example 4: The room temperature tensile stress-strain curve of the sample is shown below. Figure 5 As shown, it can be seen that: (CoCrNi) 93 The rolled Al3Ti3Nb1 sample has a tensile yield strength of 1512 MPa, a tensile ultimate strength of 1629 MPa, and a uniform elongation of approximately 2.30%. After annealing at 1000 ℃ for 1 h and aging at 700 ℃ for 1 h, the tensile yield strength is 1112 MPa, the ultimate tensile strength is 1443 MPa, and the uniform elongation is approximately 17.30%. After annealing at 1000 ℃ for 1 h and aging at 800 ℃ for 1 h, the tensile strength is 1169 MPa, the ultimate tensile strength is 1490 MPa, and the uniform elongation is approximately 12.10%.

[0060] (CoCrNi) 91 The rolled Al3Ti3Nb3 sample has a tensile yield strength of 1770 MPa, a tensile ultimate strength of 1818 MPa, and a uniform elongation of approximately 2.40%. (CoCrNi) 91 After annealing at 1000 ℃ / 1 h and aging at 700 ℃ / 1 h, Al3Ti3Nb3 has a tensile yield strength of 1244 MPa, a tensile ultimate strength of 1244 MPa, and a uniform elongation of approximately 1.12%.

[0061] As shown in the figure, when the Nb addition is 1 at.%, the resulting alloy exhibits a good strength-ductility balance after both annealing and aging heat treatments. The optimal annealing parameters are 1000 ℃ / 1 h and the optimal aging parameters are 700 ℃ / 1 h. When the Nb addition is 3 at.%, the resulting alloy exhibits greater brittleness and poorer elongation after annealing and aging heat treatments. Therefore, the optimal Nb addition is 1 at.%.

[0062] Experimental Example 5: Annealing at 1000 ℃ / 1 h and aging at 700 ℃ / 1 h (CoCrNi) 93 Al3Ti3Nb1 and (CoCrNi) 91 The tensile fracture surface SEM morphology of the Al3Ti3Nb3 sample is as follows: Figure 6 As shown, (CoCrNi) 93 The Al3Ti3Nb1 sample exhibits numerous dimples on its fracture surface, with obvious tear ridges observed; the primary fracture mode is ductile fracture. (CoCrNi) 91 No dimples were found on the fracture surface of the Al3Ti3Nb3 sample. Figure 6 The red arrows indicate the presence of cracks extending along grain boundaries or within grains, and the fracture morphology exhibits an irregular, rock-like pattern, indicating that the fracture mode is brittle fracture.

[0063] In summary, this application establishes a dual heterogeneous structure with grain size and precipitates through a cold rolling + annealing + heat treatment process, while avoiding the formation of brittle precipitates at grain boundaries, thus ensuring high strength and good uniform elongation.

[0064] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A high-strength (CoCrNi) compound 94-x Al3Ti3Nb x A method for preparing multi-principal element alloys, characterized in that, Includes the following steps: A variety of elemental metals are subjected to vacuum arc melting to obtain alloy ingots; the elemental metals include Co, Cr, Ni, Al, Ti and Nb. The alloy ingot was subjected to solution heat treatment at 1200 °C and held at this temperature for 2 hours, and then quenched in water to cool to room temperature. Then, cold rolling is performed to obtain alloy sheets; The alloy sheet was subjected to annealing and aging treatments in sequence to obtain (CoCrNi). 94-x Al3Ti3Nb x Multi-principal element alloy, 1≤x≤3, the content of each element is expressed as atomic percentage; The total reduction in the cold rolling process is 80%-90%; The annealing process is carried out at a temperature of 900℃-1050℃ for a time of 60 min-240 min, followed by water quenching and cooling. The aging treatment is carried out at a temperature of 600℃-800℃ for a time of 10 min-240 min, followed by quenching and cooling in water.

2. The high-strength (CoCrNi) according to claim 1 94-x Al3Ti3Nb x A method for preparing multi-principal element alloys, characterized in that, The process of vacuum arc melting multiple elemental metal raw materials to obtain alloy ingots includes: The various metal elemental raw materials are placed in a vacuum arc melting furnace for vacuum arc melting treatment; wherein Al is placed at the bottom, Co, Ni and Ti are placed in the middle, and Nb and Cr are placed at the top.

3. The high-strength (CoCrNi) according to claim 1 94-x Al3Ti3Nb x A method for preparing multi-principal element alloys, characterized in that, The vacuum arc melting process includes: Close the melting chamber and evacuate to a vacuum of 5×10⁻⁶. -5 Below Pa, argon gas is introduced to -0.05 MPa, and the process of evacuation and argon gas introduction is repeated three times; Set the current to 380 A-400 A, melt Ti for 60 seconds and turn it over, repeating this process three times to remove residual oxygen in the furnace. Then, melt the elemental metals Co, Cr, Ni, Al, Ti, and Nb according to a preset ratio for 60-180 seconds, turning and melting five times to ensure the metal block is completely melted. After melting, pour the alloy melt into a copper mold and let it cool to room temperature in the furnace before taking a sample.

4. A high-strength (CoCrNi) compound 94-x Al3Ti3Nb x Multi-principal element alloy, characterized in that, Prepared by the method described in any one of claims 1-3.

5. The high-strength (CoCrNi) according to claim 4 94-x Al3Ti3Nb x Multi-principal element alloy, characterized in that, The high strength (CoCrNi) 94-x Al3Ti3Nb x The multi-principal-element alloy consists of fully recrystallized coarse grains and incompletely recrystallized fine grains. The average grain size of the fully recrystallized coarse grains is 13.06 μm, and the average grain size of the incompletely recrystallized fine grains is 2.67 μm.

6. The high-strength (CoCrNi) according to claim 4 94-x Al3Ti3Nb x Multi-principal element alloy, characterized in that, The high strength (CoCrNi) 94-x Al3Ti3Nb x The tensile yield strength of the multi-principal element alloy is 1112 MPa-1169 MPa; the tensile ultimate strength is 1443 MPa-1490 MPa; and the uniform elongation is 12.10%-17.30%.

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