A cryogenic rolling and heat treatment method of high-strength FeCoNiAlTa multi-principal element alloy

Abstract

The application discloses a high-strength FeCoNiAlTa multi-main-element alloy cryogenic rolling and heat treatment method, and the multi-main-element alloy is obtained by vacuum induction melting, solid solution treatment, hot rolling, cold rolling, annealing and aging treatment, deep cryogenic rolling and medium-temperature short-time annealing. 35 Co 29 Ni 24 Al 10 Ta2 alloy. The application has the advantages of simple method, low cost, and the obtained alloy material has a strength far higher than that of a traditional cold-rolled alloy material.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials technology, specifically relating to a method for cryogenic rolling and heat treatment of high-strength FeCoNiAlTa multi-principal-element alloys. Background Technology

[0002] Multi-principal element alloys, as a new type of material, break through the traditional design concept of alloys using a single or two elements as the matrix and alloying with a small number of elements. With their unique high entropy effect, they exhibit a series of superior properties that far exceed those of conventional alloys. They show broad application prospects and huge development potential in high-end manufacturing and cutting-edge technology fields such as key structural components in aerospace, materials for service in extreme environments in the nuclear industry, and biomedical implants. They have become an important hot topic in new materials research and engineering applications.

[0003] It is worth noting that multi-principal alloys composed of a single phase often face significant "inverse relationship" bottlenecks in specific performance dimensions. Specifically, FCC single-phase alloys typically possess good ductility and formability due to their abundant slip systems, but their yield strength is often relatively insufficient. Conversely, BCC single-phase alloys, while exhibiting significant strength advantages due to higher lattice friction stress, generally suffer from low room-temperature plasticity reserves and poor work hardening ability. Two-phase multi-principal alloys cleverly couple the high plasticity and toughness brought by the FCC structure with the high strength contributed by the BCC structure, achieving a complementary balance between their respective performance advantages and disadvantages. Recent studies have shown that FCC+BCC two-phase multi-principal alloys, under specific compositional design and process control, can achieve a synergistic improvement and good balance between fracture toughness and rheological stress that is difficult for single-phase alloys to achieve.

[0004] Inducing controllable solid-state phase transformations through thermodynamic or kinetic means, and then finely controlling the phase ratio, grain size, morphology, and distribution within the material to achieve an excellent balance between strength and plasticity, has gradually become a feasible technical path and key breakthrough for overcoming the traditional opposition between strength and plasticity. In-depth research on the design of multi-principal alloy dual-phase structures based on phase transformation control and their strengthening and toughening mechanisms not only provides important theoretical support for breaking through the performance limits of such materials, but also opens up new methodological strategies for developing advanced structural materials with both high strength and good plasticity for extreme service environments. Summary of the Invention

[0005] The purpose of this invention is to provide a method for cryogenic rolling and heat treatment of high-strength FeCoNiAlTa multi-principal element alloys. By performing cryogenic rolling after aging treatment and subsequent medium-temperature short-time annealing, the room-temperature mechanical properties are significantly improved. Compared with traditional cold rolling processes, the alloy obtained by this invention exhibits extremely high yield strength and tensile strength while maintaining considerable uniform elongation.

[0006] The technical solution for achieving the objective of this invention is implemented as follows:

[0007] In a first aspect, the present invention provides a method for cryogenic rolling and heat treatment of a high-strength FeCoNiAlTa multi-principal element alloy, comprising the following steps:

[0008] S1 was prepared using vacuum induction melting to produce FeCoNiAlTa multi-principal-element alloy ingots;

[0009] S2 is used to perform solid solution treatment on the obtained alloy ingot;

[0010] S3 is hot rolled in multiple passes at 1250±20℃ and then quenched in water; then heated to 1180℃ and held for 4 minutes, quenched in water, and cold rolled in multiple passes at room temperature.

[0011] S4 annealed the cold-rolled alloy at 1180℃ for 4 minutes, followed by water quenching.

[0012] S5 is used to age the annealed alloy at 750℃ for 1 hour, followed by water quenching.

[0013] S6 immerses the aged alloy in liquid nitrogen. After the temperature stabilizes, the alloy is removed from the liquid nitrogen and immediately subjected to cryogenic rolling. After each rolling pass, the alloy is re-immersed in liquid nitrogen and the rolling process is repeated after the temperature stabilizes.

[0014] S7 involves cold-rolling the alloy and then annealing it at 750℃ for 1 hour using a medium-temperature short-time annealing process followed by water quenching.

[0015] Furthermore, based on atomic percentage, the chemical composition of this high-strength FeCoNiAlTa multi-principal element alloy is as follows: Fe 35 Co 29 Ni 24 Al 10 Ta2 (at.%).

[0016] Furthermore, in S1, high-purity metals such as Fe, Co, Ni, Al, and Ta in granular or flake form are used as raw materials; the purity is ≥99.9 wt.%.

[0017] Furthermore, in S2, the solution treatment of the obtained alloy ingot refers to solution treatment at 1250℃ for 2 hours under vacuum, followed by water quenching.

[0018] Furthermore, in S3, the total deformation of multi-pass hot rolling is 60%; the total deformation of multi-pass cold rolling is 40%.

[0019] Furthermore, in S6, the aged alloy is immersed in liquid nitrogen for at least 30 minutes. After the temperature stabilizes, the alloy is taken out of the liquid nitrogen and rolled immediately. After each rolling pass, the alloy is immersed in liquid nitrogen again. After the temperature stabilizes, the rolling process is repeated. The total deformation is 10~30%.

[0020] Compared with the prior art, the beneficial technical effects of the present invention are:

[0021] (1) The alloy prepared by the present invention can be pre-formed with a three-phase structure of “FCC+L12+B2” through deep cryogenic rolling and heat treatment processes, so that the alloy can obtain excellent comprehensive mechanical properties.

[0022] (2) The method of the present invention is simple and easy to implement, and has low cost. It only requires adjusting the rolling process and heat treatment process to achieve a significant improvement in alloy performance, which is convenient for large-scale production and industrial application. Attached Figure Description

[0023] Figure 1 This is a macroscopic morphology diagram of the alloy used in this invention after hot rolling;

[0024] Figure 2 These are the XRD patterns of samples from (a) Examples 1, 2, and Comparative Examples 1-3 of the present invention, and (b) the XRD patterns of samples from Comparative Example 4 and Comparative Example 5.

[0025] Figure 3 These are EBSD phase distribution diagrams of Embodiments 1, 2, and Comparative Examples 1-3 of the present invention;

[0026] Figure 4 These are the engineering stress-strain curves of Embodiment 1, Embodiment 2, and Comparative Examples 1 to 5 of the present invention. Detailed Implementation

[0027] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this disclosure and should not be regarded as specific limitations on this application.

[0028] It should be noted that, unless otherwise specified in the examples, the conditions should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0029] The reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0030] The technical term "and / or" in this application is only a description of the relationship between related objects, indicating that there can be three kinds of relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0031] In addition, the character " / " in this application generally indicates that the objects before and after it are in an "or" relationship.

[0032] Example 1:

[0033] Fe 35 Co 29 Ni 24 Al 10 250g of Ta2 (at.%) alloy was prepared by the following steps:

[0034] Step 1: Raw Material Preparation: Use granular Fe, Co, Ni, Al, and flake Ta high-purity metals as raw materials, with a purity ≥99.9 wt.%. Prepare the ingredients according to the specified proportions and mix them thoroughly. The mass error of each raw material during weighing is ±0.05 g. A small amount of Al will volatilize during the smelting process; the Al compensation is 3%. Mix the ingredients thoroughly.

[0035] Step 2, Melting: The alloy is prepared using the vacuum induction method. The prepared raw materials are arranged in the crucible in order of melting point (high melting point materials at the bottom, low melting point materials at the top), with Al raw materials arranged in the middle of the other materials. The protective cover is sealed, and after vacuuming, argon gas is introduced as a protective gas. The melting is carried out by electricity. The ingot is turned over and remelted twice during the melting process, and then poured into a magnesium oxide mold.

[0036] Step 3, Solution treatment of the alloy: The smelted ingot is solution treated at 1250℃ for 2 hours in a vacuum environment, followed by water quenching;

[0037] Step 4, Alloy Rolling: Hot Rolling: Perform multi-pass hot rolling at 1250±20℃, followed by water quenching; the total deformation of the multi-pass hot rolling is 60%.

[0038] Cold rolling: The hot-rolled alloy is held at 1180℃ for 4 minutes and then water-quenched; subsequently, it is cold-rolled in multiple passes at room temperature; the total deformation of the multiple cold rolling passes is 40%.

[0039] Step 5: Annealing treatment: The cold-rolled alloy is annealed at 1180℃ for 4 minutes and then water-quenched.

[0040] Step 6: Aging treatment: The annealed alloy is aged at 750℃ for 1 hour and then water quenched.

[0041] Step 7, Cryogenic Rolling: Immerse the heat-treated alloy in liquid nitrogen for at least 30 minutes. Once the temperature stabilizes (the alloy surface no longer shows "bubbling"), remove the alloy from the liquid nitrogen and immediately roll it. After each rolling pass, immerse the alloy back in liquid nitrogen and repeat the rolling process once the temperature stabilizes. The total reduction in cryogenic rolling is 30%.

[0042] Step 8, Medium-temperature short-time annealing: The cryogenically rolled alloy is held at 750℃ for 1 hour for medium-temperature short-time annealing, followed by water quenching.

[0043] Example 2:

[0044] Fe 35 Co 29 Ni 24 Al 10 250g of Ta2 (at.%) alloy was prepared using the same method as in Example 1, except that the total reduction in cryogenic rolling in step seven was changed to 10%.

[0045] Comparative Example 1:

[0046] Fe 35 Co 29 Ni 24 Al 10 250g of Ta2 (at.%) alloy was prepared using the same method as in Example 1, except that the total reduction in cryogenic rolling in step seven was changed to 20%.

[0047] Comparative Example 2:

[0048] Fe 35 Co 29 Ni 24 Al 10 250g of Ta2 (at.%) alloy was prepared according to Example 1, with the only difference being that the intermediate-temperature short-time annealing treatment in step eight was not performed after cryogenic rolling.

[0049] Comparative Example 3:

[0050] Fe 35 Co 29 Ni 24 Al 10 250g of Ta2 (at.%) alloy was prepared using the same method as in Example 1, except that only the first six steps were performed.

[0051] Comparative Example 4:

[0052] Fe 35 Co 29 Ni 24 Al 10250g of Ta2 (at.%) alloy was prepared using the same method as in Example 1, except that the aging treatment in step six was omitted.

[0053] Comparative Example 5:

[0054] Fe 35 Co 29 Ni 24 Al 10 250g of Ta2 (at.%) alloy was prepared using the same method as in Example 1, except that the aging treatment in step six and the medium-temperature short-time annealing treatment in step eight were omitted.

[0055] Figure 1 This is a macroscopic morphology diagram of the alloy used in this invention after hot rolling.

[0056] Figure 2 (a) in the figure is the XRD pattern of Embodiment 1, Embodiment 2, and Comparative Examples 1-3 of the present invention. Figure 2 (b) shows the XRD patterns of Comparative Examples 4 and 5 of this invention. The difference between the two is that the former uses a Co target and the latter uses a Cu target for XRD characterization. As can be seen from the figure, the alloy obtained by the traditional rolling and heat treatment process (Comparative Example 3) has only a weak BCC (110) peak; while the deep cryogenic rolling process after aging treatment shown in this invention (Comparative Example 2) can pre-place the BCC phase, and the BCC (110) peak is significantly enhanced compared with that before deep cryogenic rolling, indicating that the FCC→BCC phase transformation occurred during the deep cryogenic deformation process; after deep cryogenic rolling, the alloy obtained by medium-temperature short-time annealing treatment (Example 1, Example 2, Comparative Example 1) can be observed from the XRD characterization results to have a strong (100) peak, indicating that the B2 phase appears during the heat treatment process. It is worth noting that the alloy is annealed after cold rolling but not aged, and then directly subjected to deep cold rolling (Comparative Example 4) cannot pre-place the BCC phase; while the BCC (110) peak appears in Comparative Example 5 because the subsequent heat treatment process produces precipitates.

[0057] Figure 3 These are EBSD phase distribution diagrams for Examples 1, 2, and Comparative Examples 1-3 of the present invention. As can be seen from the diagrams, the alloy matrix obtained by conventional rolling and heat treatment processes (Comparative Example 3) has an FCC structure; after aging treatment and cryogenic rolling (Comparative Example 2), the BCC phase was successfully pre-placed, resulting in an FCC+BCC structure; after medium-temperature short-time annealing (Example 1), the BCC phase content decreased.

[0058] Figure 4These are the engineering stress-strain curves of Examples 1, 2, and Comparative Examples 1-5 of this invention. The alloy obtained by conventional rolling and heat treatment processes (Comparative Example 3), while exhibiting good elongation, has low yield strength and tensile strength. The alloy obtained by cryogenic rolling after aging treatment (Comparative Example 2) shows a significant improvement in strength, with a yield strength reaching 1701 MPa and a tensile strength reaching 1744 MPa, but the alloy lacks uniform elongation. However, after cryogenic rolling followed by medium-temperature short-time annealing (Examples 1, 2, and Comparative Example 1), the uniform elongation is significantly improved; the alloys obtained by cryogenic rolling with 30% rolling weight (Example 1) and cryogenic rolling with 10% rolling weight (Example 2) exhibit excellent comprehensive properties. It is particularly important to note that aging treatment before cryogenic rolling is an indispensable step in the process of this invention. Without aging treatment, direct cryogenic rolling cannot pre-establish the BCC phase, which is the key reason why the mechanical properties of Comparative Examples 4 and 5 are inferior to those of the examples.

[0059] The mechanical properties of the alloys in all embodiments and comparative examples are shown in Table 1:

[0060] Table 1

[0061]

[0062] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A method for cryogenic rolling and heat treatment of a high-strength FeCoNiAlTa multi-principal element alloy, characterized in that, Includes the following steps: S1 was prepared using vacuum induction melting to produce FeCoNiAlTa multi-principal-element alloy ingots; S2 is used to perform solid solution treatment on the obtained alloy ingot; S3 is hot rolled in multiple passes at 1250±20℃ and then water quenched; then heated to 1180℃ and held for 4 minutes, water quenched, and cold rolled in multiple passes at room temperature. S4 annealed the cold-rolled alloy at 1180℃ for 4 minutes, followed by water quenching. S5 is used to age the annealed alloy at 750℃ for 1 hour, followed by water quenching. S6 immerses the aged alloy in liquid nitrogen. After the temperature stabilizes, the alloy is removed from the liquid nitrogen and immediately subjected to cryogenic rolling. After each rolling pass, the alloy is re-immersed in liquid nitrogen and the rolling process is repeated after the temperature stabilizes. S7 involves cold-rolling the alloy and then holding it at 750℃ for 1 hour for medium-temperature short-time annealing followed by water quenching.

2. The method as described in claim 1, characterized in that, The chemical composition of this high-strength FeCoNiAlTa multi-principal element alloy, based on atomic percentage, is as follows: Fe 35 Co 29 Ni 24 Al 10 Ta2.

3. The method as described in claim 1, characterized in that, In S1, high-purity metals such as Fe, Co, Ni, Al, and Ta in granular or flake form are used as raw materials; the purity is ≥99.9 wt.%.

4. The method as described in claim 1, characterized in that, In S2, the solution treatment of the obtained alloy ingot refers to solution treatment at 1250℃ for 2 hours under vacuum, followed by water quenching.

5. The method as described in claim 1, characterized in that, In S3, the total deformation of multi-pass hot rolling is 60%; the total deformation of multi-pass cold rolling is 40%.

6. The method as described in claim 1, characterized in that, In S6, the aged alloy is immersed in liquid nitrogen for at least 30 minutes. After the temperature stabilizes, the alloy is taken out of the liquid nitrogen and rolled immediately. After each rolling pass, the alloy is immersed in liquid nitrogen again. After the temperature stabilizes, the rolling process is repeated. The total deformation is 10~30%.

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