A heterogeneous structure nickel-rich high entropy alloy and its preparation process

Abstract

The present invention discloses a heterogeneous structure nickel-rich high entropy alloy and a preparation process thereof, and relates to the technical field of alloys. The present invention adopts a cold rolling combined with a two-step furnace cold annealing process to prepare a nickel-rich high entropy alloy Ni 46.23 Co 23 Cr 10 Fe5Al 8.5 Ti4W2Mo1C 0.15 B 0.1 Zr 0.02 By treating the alloy, a new type of nickel-rich high-entropy alloy with a dual heterogeneous layered structure of grains / precipitation phases and a serrated grain boundary / phase boundary composite structure was prepared. The alloy material has good mechanical properties in a wide temperature range (-196~700℃), which can meet the high-performance use requirements of the alloy material.

Description

Technical Field

[0001] The present invention relates to the technical field of alloys, and in particular to a heterogeneous structure nickel-rich high entropy alloy and a preparation process thereof. Background Art

[0002] In the process of developing advanced structural materials that can withstand extreme conditions such as outer space exploration, deep-sea oil production and aerospace, the demand for excellent mechanical and environmental properties over a wide temperature range continues to grow. However, due to the inherent conflict between material properties, such as strength and ductility, achieving these excellent mechanical properties The combination is still highly challenging. Most mechanisms for material strengthening and toughening are only effective within a specific temperature range, and their strengthening effects often weaken or even have adverse effects beyond the specific temperature range. A typical example is the strengthening induced by single grain heterostructures. For example, by introducing single grain heterostructures into low-strength face-centered cubic high-entropy alloys, the resulting single grain heterostructure high-entropy alloys exhibit significantly enhanced strength at both room temperature and low temperature due to the strong heterogeneous deformation induced effect, while maintaining or minimally reducing the ductility of the alloy. However, at high temperatures, the single grain heterostructure is susceptible to grain growth, resulting in a weakening and rapid decay of the heterogeneous deformation induced effect.

[0003] In order to improve the strengthening effect of the heterogeneous deformation induced effect at high temperature, a dispersed L1 2The nano-precipitated phase of the structure can form a dual heterogeneous structure precipitation-strengthened high entropy alloy of grains and precipitates. Due to the synergistic effect of the heterogeneous deformation-induced effect and the precipitation strengthening effect, the synthesized dual heterogeneous structure precipitation-strengthened high entropy alloy of grains and precipitates not only exhibits high strength and good ductility at low temperature and room temperature, and its strength is significantly better than that of the single heterogeneous structure high entropy alloy of grains, but also shows obvious thermal stability and strength increase at high temperature. In addition, with the increase of temperature, another serious problem, that is, the medium-temperature brittleness of the material is also significantly suppressed, resulting in a transition from brittleness to toughness. The basic principle of suppressing medium-temperature brittleness is that the grain heterogeneous structure composed of recrystallized grains and deformed grains of the dual heterogeneous structure of grains and precipitates effectively suppresses the nucleation and propagation of cracks along the grain boundaries. Since these synergistic strengthening effects and toughening mechanisms can be effective at different temperatures, the dual heterogeneous structure of grains and precipitates has become a new material design strategy that can improve the mechanical properties of materials in a wide temperature range. However, the improved elongation of the grain-precipitation dual heterostructure precipitation-strengthened high entropy alloy at intermediate temperature is mainly the non-uniform elongation during necking, and the uniform elongation is still very low. This situation has poor resistance to accidental overload, which in turn poses a potential threat to the safety and reliability of the material during long-term use. Therefore, the lack of uniform elongation at intermediate temperature is a key issue that urgently needs to be further addressed in the grain-precipitation dual heterostructure precipitation-strengthened high entropy alloy. Summary of the invention

[0004] The purpose of the present invention is to provide a heterogeneous structure nickel-rich high entropy alloy and a preparation process thereof to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for preparing a heterogeneous nickel-rich high entropy alloy comprises the following steps:

[0007] (1) Homogenization treatment: The multi-element nickel-rich high entropy alloy Ni 46.23 Co 23 Cr 10 Fe 5 Al 8.5 Ti 4 W 2 Mo 1 C 0.15 B 0.1 Zr 0.02 Homogenization treatment was performed at 1150-1250°C, followed by cooling to room temperature at a cooling rate of 1.5-2.5°C / min;

[0008] (2) Cold rolling treatment: The multi-principal element nickel-rich high entropy alloy Ni 46.23 Co23 Cr 10 Fe 5 Al 8.5 Ti 4 W 2 Mo 1 C 0.15 B 0.1 Zr 0.02 Perform several cold rolling processes;

[0009] (3) Two-step furnace cold annealing treatment: The multi-principal element nickel-rich high entropy alloy Ni 46.23 Co 23 Cr 10 Fe 5 Al 8.5 Ti 4 W 2 Mo 1 C 0.15 B 0.1 Zr 0.02 The alloy is placed in a heating furnace, heated to 1050-1100°C at a heating rate of 200-250°C / min, then cooled to 950-1000°C with the furnace at a cooling rate of 20-25°C / min, then cooled from 950-1000°C to 750-800°C with the furnace at a cooling rate of 5-10°C / min, and finally oil-cooled to room temperature to obtain the heterostructure nickel-rich high entropy alloy.

[0010] As a further preferred embodiment of the present invention, the homogenization treatment time is 4-8 hours.

[0011] As a further preferred embodiment of the present invention, the rolling rate of the cold rolling treatment is 0.05-0.15 mm / pass. Under the condition of the same total rolling reduction, the greater the single-pass reduction, the greater the dislocation accumulation, and the stronger the recrystallization driving force.

[0012] As a further preferred embodiment of the present invention, the multi-principal element nickel-rich high entropy alloy Ni 46.23 Co 23 Cr 10 Fe 5 Al 8.5 Ti 4 W 2 Mo 1 C 0.15 B 0.1 Zr 0.02 The alloy raw materials are mixed and smelted, and then prepared by suction casting in a water-cooled copper mold.

[0013] As a further preferred embodiment of the present invention, the mixed melting of the alloy raw materials is carried out under an argon atmosphere.

[0014] More preferably, the preset size of the water-cooled copper mold is 50 mm×10 mm×5 mm, and the thickness of the alloy after cold rolling is 1.5 mm.

[0015] In the present invention, the multi-principal element nickel-rich high entropy alloy Ni 46.23 Co 23 Cr 10 Fe 5 Al 8.5 Ti 4 W 2 Mo 1 C 0.15 B 0.1 Zr 0.02 The melting point is 1314℃, and the dissolution temperature of the precipitated phase is 1130℃.

[0016] The present invention also provides a heterogeneous structure nickel-rich high entropy alloy prepared by the above preparation method.

[0017] Adjusting the structure of nickel-rich high-entropy alloys from spherical precipitation phases and straight grain boundaries to irregular precipitation phases and serrated grain boundaries can effectively improve high-temperature uniform ductility while slowing down intergranular cracking. Based on the design strategy of the composite structure, the present invention combines the dual heterogeneous layered structure of grains / precipitation phases with serrated grain boundaries / phase boundaries to prepare nickel-rich high-entropy alloys with high yield strength and uniform ductility in a wide temperature range, especially the strain hardening ability at medium temperatures is also improved.

[0018] The cold rolling treatment first performed in the present invention is to introduce partial recrystallization in the subsequent annealing, promote the formation of deformed grain / recrystallized grain isomerism and a layered structure composed of recrystallized lamellae and deformed grain lamellae. The two-step furnace cold annealing treatment after cold rolling is mainly to promote the formation of serrated grain boundaries / phase boundaries. The double isomerism of grains / precipitated phases formed by the cold rolling plus two-step furnace cold annealing process of the present invention can bring about a strong heterogeneous deformation effect and improve the yield strength of the sample. In addition, the layered structure composed of the deformed grain lamellae and the recrystallized grain lamellae and the serrated grain boundaries / phase boundaries can play a two-level strain delocalization role and improve the uniform elongation of the sample.

[0019] The present invention discloses the following technical effects:

[0020] The present invention adopts cold rolling combined with a two-step furnace cold annealing process to prepare a new nickel-rich high-entropy alloy with a dual heterogeneous layered structure of grains / precipitated phases and a serrated grain boundary / phase boundary composite structure. The alloy material has good mechanical properties in a wide temperature range (-196 to 700°C) and can meet the high-performance use requirements of the alloy material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 This is a flow chart for preparing a high-entropy high-temperature alloy having a grain / precipitation phase dual heterogeneous layered structure and a serrated grain boundary / phase boundary composite structure in Example 1 of the present invention.

[0023] Figure 2 1 and 1 are tensile engineering stress-strain curves of the alloy materials prepared in Example 1 and Comparative Example 1 of the present invention; wherein, (a) is the tensile engineering stress-strain curve of the alloy materials prepared in Example 1 and Comparative Example 1 at -196°C, (b) is the tensile engineering stress-strain curve of the alloy materials prepared in Example 1 and Comparative Example 1 at 25°C, and (c) is the tensile engineering stress-strain curve of the alloy materials prepared in Example 1 and Comparative Example 1 at 700°C.

[0024] Figure 3 The backscattered electron diffraction pattern and the scanning electron diffraction pattern of the high entropy superalloy having a grain / precipitation phase dual heterogeneous layered structure and a serrated grain boundary / phase boundary composite structure in Example 1 of the present invention are shown. Among them, (a) is a backscattered electron diffraction pattern, (b) is a scanning electron pattern of a recrystallized region, and (c) is a scanning electron pattern of a deformed grain region.

[0025] Figure 4 The backscattered electron diffraction analysis diagram (a) and scanning electron diagram (b) of the nickel-rich high entropy alloy with uniform grains and precipitated phase structure prepared in Comparative Example 1. DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0028] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0029] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] In the present invention, "room temperature" specifically refers to 25°C.

[0032] Example 1

[0033] The alloy composition of nickel-rich high entropy alloy is Ni 46.23 Co 23 Cr 10 Fe 5 Al 8.5 Ti 4 W 2 Mo 1 C 0.15 B 0.1 Zr 0.02 The atomic percentage and mass percentage of each element are shown in Table 1.

[0034] Table 1

[0035] element Atomic Percent Mass percentage Ni 46.23 47.13 Co 23 23.54 Cr 10 9.03 Fe 5 4.85 Al 8.5 3.97 Ti 4 3.33 W 2 6.39 Mo 1 1.67 C 0.15 0.03 B 0.1 0.02 Zr 0.02 0.03

[0036] (1) Raw material weighing: The alloy raw material ratio is made according to the mass ratio of each element in Table 1: Select raw materials with a purity of 99.99%, clean the oxide scale on the surface of the raw materials, then ultrasonically clean them with acetone, use a hair dryer to dry them, and use a balance with an accuracy of 0.001g to weigh the raw materials.

[0037] (2) Arc melting: Place the weighed raw materials in the order of melting point from low to high and size from small to large into a water-cooled non-consumable vacuum arc melting furnace, evacuate to below 0.005Pa, fill with high-purity argon, flush the furnace chamber, repeat three times, and then open the arc under the protection of high-purity argon, so that the initial arc current is 80A, and gradually increase to 150A to melt the titanium ingot; then move to the raw materials to be melted, gradually melt the raw materials along the water-cooled copper crucible, and then increase the current to 200A, stay for about 10s, so that the alloy melts into button ingots. Then, after repeated melting for 2 times, turn on the electromagnetic stirring function of the arc for the third melting. Arc stirring can make the alloy melt more evenly, and the more difficult to melt parts inside will be fully melted and diffused with stirring. Repeat the melting for 2 more times, turn off the electromagnetic stirring, and melt again, and ensure at least five times, so that the alloy components are fully melted and diffused evenly.

[0038] (3) Copper mold suction casting: The fully molten alloy is kept at an arc of 300A for 10s, and the melt is then sucked into a designed plate-shaped water-cooled copper mold (10mm wide, 5mm thick, 50mm high) to obtain a plate-shaped sample with a thickness of 5mm.

[0039] (4) Homogenization treatment: The obtained 5 mm thick plate-shaped nickel-rich high-entropy alloy sample was placed in a muffle furnace for homogenization treatment, kept at 1200°C for 4 h, and then cooled to room temperature at 2°C / min.

[0040] (5) Cold rolling: The homogenized sample was cold rolled 30 times to a thickness of 1.5 mm.

[0041] (6) Two-step furnace cooling annealing treatment: The rolled sample is placed in a muffle furnace and heated to 1100°C at a heating rate of 220°C / min, then furnace cooled to 1000°C at a cooling rate of 25°C / min, then furnace cooled from 1000°C to 800°C at a cooling rate of 8°C / min, and finally oil cooled to room temperature to obtain a high-entropy high-temperature alloy with a dual heterogeneous layered structure of grains / precipitation phases and a serrated grain boundary / phase boundary composite structure.

[0042] (7) Wire cutting is performed on the high-entropy high-temperature alloy sample having a dual heterogeneous layered structure of grains / precipitation phases and a serrated grain boundary / phase boundary composite structure obtained in step (6) to obtain a test specimen.

[0043] Figure 1 This is a flow chart for preparing a high-entropy high-temperature alloy having a grain / precipitation phase dual heterogeneous layered structure and a serrated grain boundary / phase boundary composite structure in Example 1 of the present invention.

[0044] Figure 3The backscattered electron diffraction pattern and the scanning electron diffraction pattern of the high entropy superalloy having a grain / precipitation phase dual heterogeneous layered structure and a serrated grain boundary / phase boundary composite structure in Example 1 of the present invention are shown. Among them, (a) is a backscattered electron diffraction pattern, (b) is a scanning electron pattern of a recrystallized region, and (c) is a scanning electron pattern of a deformed grain region.

[0045] from Figure 3 It can be seen that the heterogeneous alloy material prepared in Example 1 has a new type of grain / precipitation phase dual heterogeneous layered structure of deformed grains / recrystallized grains, spherical precipitate phases / irregular precipitate phases, serrated grain boundaries / phase boundaries, and a serrated grain boundary / phase boundary composite structure of recrystallized grain lamellae and deformed grain lamellae.

[0046] Comparative Example 1

[0047] The only difference from Example 1 is the heat treatment method after copper mold suction casting, which is as follows:

[0048] Steps (1) to (3) are the same as in Example 1;

[0049] (4) Homogenization treatment: The obtained 5 mm thick plate-shaped nickel-rich high-entropy alloy sample was placed in a muffle furnace for homogenization treatment, kept at 1200°C for 4 h, and then directly oil-cooled to room temperature.

[0050] (5) Aging treatment: The sample after homogenization treatment in step (4) is isothermally aged at 800°C for 16 h, and then directly oil-cooled to room temperature to obtain a nickel-rich high-entropy alloy with uniform grains and precipitation phase structure.

[0051] (6) Wire cutting the nickel-rich high-entropy alloy with uniform grain and precipitation phase structure obtained in step (5) to obtain a sample.

[0052] The backscattered electron diffraction pattern (a) and the scanning electron pattern (b) obtained in Comparative Example 1 of the present invention are as follows: Figure 4 shown.

[0053] Depend on Figure 4 It can be seen that the alloy material treated by the method of Comparative Example 1 has uniform equiaxed grains and spherical precipitation phase structure.

[0054] The alloy materials prepared in Example 1 and Comparative Example 1 were subjected to tensile mechanics tests at -196°C, 25°C and 700°C:

[0055] The tensile tests at -196℃ and 25℃ were completed on an MTS-CMT5205 universal mechanical testing machine. The gauge length of the tensile specimen was 12.8mm, the gauge length of the extensometer was 10mm, and the strain rate was 0.77mm / min.

[0056] The 700°C tensile test was completed on an Instron servo hydraulic press equipped with a high-temperature heating furnace. The gauge length of the tensile specimen was 12.8 mm and the strain rate was 0.77 mm / min.

[0057] The tensile engineering stress-strain curves of the alloy materials prepared in Example 1 and Comparative Example 1 are as follows: Figure 2 As shown; wherein, (a) is the tensile engineering stress-strain curve of the alloy materials prepared in Example 1 and Comparative Example 1 at -196°C, (b) is the tensile engineering stress-strain curve of the alloy materials prepared in Example 1 and Comparative Example 1 at 25°C, and (c) is the tensile engineering stress-strain curve of the alloy materials prepared in Example 1 and Comparative Example 1 at 700°C.

[0058] Depend on Figure 2 As can be seen from (c), the heterostructure nickel-rich high entropy alloy of the present invention has excellent work hardening ability at 700°C (medium temperature).

[0059] The tensile yield strength of the heterogeneous structure nickel-rich high entropy alloy prepared in Example 1 at -196°C, 25°C and 700°C were 1421MPa, 1067MPa and 1101MPa, respectively, and the uniform elongation was 18.4%, 11.2% and 3.0%, respectively. The tensile yield strength of the alloy material prepared in Comparative Example 1 at -196°C, 25°C and 700°C were 851MPa, 808MPa and 713MPa, respectively, and the uniform elongation was 12.8%, 11.4% and 0.6%, respectively.

[0060] It can be seen that the heterostructure nickel-rich high entropy alloy prepared in Example 1 of the present invention has high yield strength and uniform elongation in a wide temperature range.

[0061] The present invention utilizes a heat treatment process of cold rolling plus two-step furnace cold annealing to prepare a novel nickel-rich high-entropy alloy with a dual heterogeneous layered structure of grains / precipitated phases and a serrated grain boundary / phase boundary composite structure. The nickel-rich high-entropy alloy has excellent mechanical properties and uniform elongation in a wide temperature range.

[0062] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a heterogeneous nickel-rich high entropy alloy, characterized in that: The following steps are involved: (1) Homogenization treatment: The multi-element nickel-rich high entropy alloy Ni 46.23 Co 23 Cr 10 Fe5Al 8.5 Ti4W2Mo1C 0.15 B 0.1 Zr 0.02 Homogenization treatment was performed at 1150-1250°C, followed by cooling to room temperature at a cooling rate of 1.5-2.5°C / min; (2) Cold rolling treatment: The multi-principal element nickel-rich high entropy alloy Ni 46.23 Co 23 Cr 10 Fe5Al 8.5 Ti4W2Mo1C 0.15 B 0.1 Zr 0.02 Perform cold rolling treatment; (3) Two-step furnace cold annealing treatment: The multi-principal element nickel-rich high entropy alloy Ni 46.23 Co 23 Cr 10 Fe5Al 8.5 Ti4W2Mo1C 0.15 B 0.1 Zr 0.02 Placing in a heating furnace, heating to 1050-1100° C. at a heating rate of 200-250° C. / min, then cooling with the furnace to 950-1000° C. at a cooling rate of 20-25° C. / min, then cooling with the furnace from 950-1000° C. to 750-800° C. at a cooling rate of 5-10° C. / min, and finally oil cooling to room temperature to obtain the heterogeneous structure nickel-rich high entropy alloy; The homogenization time is 4-8h.

2. The preparation method according to claim 1, characterized in that: The rolling rate of the cold rolling process is 0.05-0.15 mm / pass.

3. The preparation method according to claim 1, characterized in that: The multi-principal element nickel-rich high entropy alloy Ni 46.23 Co 23 Cr 10 Fe5Al 8.5 Ti4W2Mo1C 0.15 B 0.1 Zr 0.02 The alloy raw materials are mixed and smelted, and then suction-casted into a water-cooled copper mold.

4. The preparation method according to claim 3, characterized in that: The alloy raw materials are mixed and smelted in an argon atmosphere.

5. A heterostructure nickel-rich high entropy alloy prepared by the preparation method according to any one of claims 1 to 4.

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