Method for improving elongation of high entropy alloy

Abstract

The present invention relates to a method for improving the elongation of a high entropy alloy, which is specifically implemented according to the following steps: prepare a high entropy alloy, first place the high entropy alloy in a vacuum heat treatment furnace and heat it to 1100°C-1200°C, and keep it warm for 2 hours-3 hours; secondly, cool the vacuum heat treatment furnace to 750°C-850°C, and keep it warm for 6 hours-10 hours; finally, cool the high entropy alloy to room temperature and take it out from the vacuum heat treatment furnace. The present invention can make the reinforcing phase fully precipitate, and the reinforcing phase finally formed is carbide+silicide, the reinforcing phase is approximately spherical, effectively controls grain growth, and improves the plasticity of the alloy; the area ratio occupied by the reinforcing phase is about 40%-50%, which has a great effect on improving plasticity; the internal stress caused by the hot isostatic pressing process can be effectively eliminated through the heat treatment process; the room temperature elongation of the high entropy alloy finally prepared can reach 15%-18%, which is significantly higher than the prior art level.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of alloy preparation, and in particular to a method for improving the elongation of a high entropy alloy. Background Art

[0002] Iron-nickel-cobalt-chromium-molybdenum high entropy alloys have become an important research branch in the high entropy alloy system due to their excellent corrosion resistance, ductility and structural stability. They are mainly used in high-temperature corrosion-resistant parts of industrial sectors such as aviation engine hot end components, space rocket engine high-temperature components and industrial gas turbines, and have important strategic significance in the fields of national economy and military. In practical applications, it is often necessary to withstand strong vibrations, riveting, knocking, etc., which requires the material to have very excellent ductility. The currently reported elongation of iron-nickel-cobalt-chromium-molybdenum high entropy alloys can reach up to 13.5%; for example, patent CN113732285B, but it cannot meet the use requirements for more demanding working conditions.

[0003] Heat treatment process is an indispensable and important means to improve the plastic toughness and corrosion resistance of alloys, eliminate stress and soften. For high-temperature alloys such as iron-based and nickel-based alloys, heat treatment has been generally used to improve performance, but there is no relevant report on using heat treatment to improve the performance of iron-nickel-cobalt-chromium-molybdenum high-entropy alloys. In reports on iron-nickel-cobalt-chromium-molybdenum high-entropy alloys, powder metallurgy preparation methods are usually used, especially hot isostatic pressing preparation methods, and their phase composition is a two-phase structure composed of a face-centered cubic matrix phase and carbide particles, and the carbide particle phase plays a strengthening role. Based on the existing iron-nickel-cobalt-chromium-molybdenum high-entropy alloys, this patent proposes a heat treatment method, so that in addition to precipitating carbides in the matrix, silicides are precipitated, so that carbides and a small amount of silicides are approximately spherical and evenly distributed in the matrix and grain boundaries. The area ratio occupied by the reinforcing phase is about 40%-50%. The final iron-nickel-cobalt-chromium-molybdenum high-entropy alloy has an elongation of 15%-18%, which is much higher than the existing technical level and meets special working conditions such as knocking, vibration, and riveting.

[0004] Based on the above, the present invention discloses a method for improving the elongation of a high entropy alloy. By adding a heat treatment process on the basis of the existing iron-nickel-cobalt-chromium-molybdenum high entropy alloy, and by selecting appropriate heat treatment process parameters, the reinforcing phase in the high entropy alloy can be fully precipitated, and finally a reinforcing phase combining carbides and silicides is formed, and the reinforcing phase is approximately spherical and uniformly precipitated at the matrix grain boundary or in the matrix. The reinforcing phase distributed at the grain boundary can play a pinning role, effectively control grain growth, and improve the plasticity of the alloy. The area ratio occupied by the reinforcing phase is about 40%-50%. And the internal stress caused by the hot isostatic pressing process can be effectively eliminated through the heat treatment process, and the room temperature elongation of the high entropy alloy finally prepared can reach 15%-18%, which is significantly higher than the existing technical level. The high entropy alloy can be applied to the high-temperature turbine end of the gas turbine, solving the problems of riveting cracking during the actual installation process, filling the domestic gap, and realizing complete localization. And it can be widely used in hot end components of aviation engines, high-temperature components of rocket engines, etc., and has important strategic significance in the fields of major equipment, national economy and military in my country.

[0005] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions.

[0006] It should be noted that this section is intended to provide background or context for the technical solutions of the present invention stated in the claims. The description herein is not admitted to be prior art by inclusion in this section. Summary of the invention

[0007] The object of the present invention is to provide a method for improving the elongation of a high entropy alloy, thereby solving one or more problems caused by the limitations and defects of the related art at least to a certain extent.

[0008] The present invention provides a method for improving the elongation of a high entropy alloy, which is specifically implemented according to the following steps:

[0009] To prepare a high entropy alloy, first place the high entropy alloy in a vacuum heat treatment furnace and heat it to 1100°C-1200°C, and keep it warm for 2 hours-3 hours; secondly, cool the vacuum heat treatment furnace to 750°C-850°C, and keep it warm for 6 hours-10 hours; finally, cool the high entropy alloy to room temperature and take it out of the vacuum heat treatment furnace.

[0010] In the present invention, the high entropy alloy is prepared by a powder metallurgy method.

[0011] In the present invention, the high entropy alloy is prepared by hot isostatic pressing.

[0012] In the present invention, the high entropy alloy is an iron-nickel-cobalt-chromium-molybdenum series high entropy alloy.

[0013] In the present invention, the alloy purity of the iron-nickel-cobalt-chromium-molybdenum series high entropy alloy is ≥99.5wt%.

[0014] In the present invention, the vacuum degree in the vacuum heat treatment furnace is 1.0×10 -2 Pa~1.0×10 -3 Pa.

[0015] In the present invention, the heating rate when the temperature in the vacuum heat treatment furnace is raised to 1100° C.-1200° C. is 7° C. / min-10° C. / min.

[0016] In the present invention, the cooling rate when the temperature in the vacuum heat treatment furnace is cooled to 750°C-850°C is 3°C / min-5°C / min.

[0017] The technical solution provided by the present invention may include the following beneficial effects:

[0018] In the present invention, by using the above method and appropriate heat treatment process parameters, the iron-nickel-cobalt-chromium-molybdenum high entropy alloy prepared by the existing powder metallurgy method, especially the hot isostatic pressing method, is heat treated. The high entropy alloy prepared by heat treatment has the following advantages:

[0019] (1) The reinforcement phase can be fully precipitated, and the final reinforcement phase is carbide + silicide. The reinforcement phase is approximately spherical and precipitates uniformly at the grain boundary of the matrix or in the matrix. The reinforcement phase distributed at the grain boundary can play a pinning role, effectively control grain growth, and improve the plasticity of the alloy;

[0020] (2) The area ratio of the reinforcement phase is about 40%-50%, which plays a great role in improving plasticity;

[0021] (3) The internal stress caused by the hot isostatic pressing process can be effectively eliminated through the heat treatment process;

[0022] (4) The room temperature elongation of the high entropy alloy treated by this method can reach 15%-18%, which is significantly higher than the existing technical level. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0024] Figure 1 A flow chart showing a method for increasing the elongation of a high entropy alloy in an exemplary embodiment of the present invention;

[0025] Figure 2 A 500-fold metallographic micrograph of the heat-treated iron-nickel-cobalt-chromium-molybdenum high entropy alloy of Example 1 of the present invention is shown;

[0026] Figure 3 The distribution diagram of the reinforcement phase annotated by the pro imaging software is shown in the 500 times metallographic micrograph of the iron-nickel-cobalt-chromium-molybdenum series high entropy alloy after heat treatment in Example 1 of the present invention;

[0027] Figure 4 The SEM energy spectrum of the microscopic enhancement phase of the iron-nickel-cobalt-chromium-molybdenum high entropy alloy after heat treatment in Example 1 of the present invention is shown at a magnification of 1000. DETAILED DESCRIPTION

[0028] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0029] In addition, the accompanying drawings are only schematic illustrations of embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0030] In this example embodiment, a method for improving the elongation of a high entropy alloy is first provided. Figure 1 As shown, the method comprises the following steps:

[0031] Step S101: prepare a high entropy alloy; the high entropy alloy is prepared by a powder metallurgy method, especially an iron-nickel-cobalt-chromium-molybdenum high entropy alloy prepared by a hot isostatic pressing method; the iron-nickel-cobalt-chromium-molybdenum high entropy alloy has an alloy purity of ≥99.5wt%.

[0032] The hot isostatic pressing process cannot achieve long-term heat preservation, so the reinforcement phase cannot be well precipitated in the matrix. In order to stably dissolve the reinforcement phase into the matrix, the iron-nickel-cobalt-chromium-molybdenum high entropy alloy prepared by hot isostatic pressing is subjected to the following heat treatment.

[0033] Step S102: Place the Fe-Ni-Co-Cr-Mo high entropy alloy in a vacuum heat treatment furnace and heat it to 1100°C-1200°C for 2-3 hours; the heating rate is 7°C / min-10°C / min; the vacuum degree in the vacuum heat treatment furnace is 1.0×10 -2 Pa~1.0×10 -3 Pa;

[0034] In step S102, if the temperature in the vacuum heat treatment furnace is less than 1100°C, it is difficult for the reinforcement phase to precipitate in the matrix, or the precipitated reinforcement phase is extremely unstable;

[0035] If the temperature is greater than 1200℃ or the holding time at this stage is too long, grain coarsening will occur, or some grain boundaries will be overburned, resulting in weakening of the grain boundaries and overburning, which will ultimately lead to a decrease in the material's plasticity or reduced mechanical properties.

[0036] In the process of heating from room temperature to 1100-1200°C, in order to save time cost, the heating rate should not be too slow, that is, controlled at 7-10°C / min.

[0037] Step S103: cool the vacuum heat treatment furnace to 750°C-850°C and keep it warm for 6 hours-10 hours; the cooling rate is 3°C / min-5°C / min.

[0038] In step S103, the temperature should not be too high, otherwise over-burning will occur. In step S103, the long-term heat preservation can ensure that the reinforcement phase is completely dissolved into the matrix and silicide is precipitated, so that the morphology of the reinforcement phase is close to spherical and can be evenly distributed in the matrix and the grain boundaries.

[0039] Long-term heat preservation can partially transform the carbide reinforcement phase into silicide, and long-term heat preservation can eliminate the internal stress generated in the alloy during the hot isostatic pressing process.

[0040] The final microstructure of the iron-nickel-cobalt-chromium-molybdenum high-entropy alloy is composed of a matrix phase and a reinforcement phase. The reinforcement phase is approximately spherical and evenly distributed in the matrix and grain boundaries. The area ratio of the reinforcement phase is about 40%-50% calculated by Pro Imaging software. The room temperature elongation after fracture is 15%-18%.

[0041] Step S104: Cool the high entropy alloy to room temperature and take it out from the vacuum heat treatment furnace.

[0042] The above method for improving the elongation of high entropy alloy was experimented, and the specific contents are as follows:

[0043] Example 1

[0044] 1: Prepare a high entropy alloy; the high entropy alloy is prepared by a powder metallurgy method, especially an iron-nickel-cobalt-chromium-molybdenum high entropy alloy prepared by a hot isostatic pressing method; the purity of the iron-nickel-cobalt-chromium-molybdenum high entropy alloy is ≥99.5wt%; the iron-nickel-cobalt-chromium-molybdenum high entropy alloy is composed of Fe, Ni, Co, Cr, Mo, C, Si, Mn, and W elements, and the remainder is unavoidable impurity elements.

[0045] 2: Place the Fe-Ni-Co-Cr-Mo high entropy alloy in a vacuum heat treatment furnace and heat it to 1100°C for 2.5 hours; the heating rate is 8°C / min; the vacuum degree in the vacuum heat treatment furnace is 1.0×10 -2 Pa;

[0046] 3: Cool the vacuum heat treatment furnace to 780°C and keep it for 9 hours; the cooling rate is 3°C / min.

[0047] 4: Cool the iron-nickel-cobalt-chromium-molybdenum high entropy alloy to room temperature and take it out from the vacuum heat treatment furnace.

[0048] Example 2

[0049] 1: Prepare a high entropy alloy; the high entropy alloy is prepared by a powder metallurgy method, especially an iron-nickel-cobalt-chromium-molybdenum high entropy alloy prepared by a hot isostatic pressing method; the purity of the iron-nickel-cobalt-chromium-molybdenum high entropy alloy is ≥99.5wt%; the iron-nickel-cobalt-chromium-molybdenum high entropy alloy is composed of Fe, Ni, Co, Cr, Mo, C, Si, Mn, and W elements, and the remainder is unavoidable impurity elements.

[0050] 2: Place the Fe-Ni-Co-Cr-Mo high entropy alloy in a vacuum heat treatment furnace and heat it to 1150°C for 2.5 hours; the heating rate is 10°C / min; the vacuum degree in the vacuum heat treatment furnace is 1.0×10 -2 Pa;

[0051] 3: Cool the vacuum heat treatment furnace to 800°C and keep it for 7.5 hours; the cooling rate is 4°C / min.

[0052] 4: Cool the iron-nickel-cobalt-chromium-molybdenum high entropy alloy to room temperature and take it out from the vacuum heat treatment furnace.

[0053] Example 3

[0054] 1: Prepare a high entropy alloy; the high entropy alloy is prepared by a powder metallurgy method, especially an iron-nickel-cobalt-chromium-molybdenum high entropy alloy prepared by a hot isostatic pressing method; the purity of the iron-nickel-cobalt-chromium-molybdenum high entropy alloy is ≥99.5wt%; the iron-nickel-cobalt-chromium-molybdenum high entropy alloy is composed of Fe, Ni, Co, Cr, Mo, C, Si, Mn, and W elements, and the remainder is unavoidable impurity elements.

[0055] 2: Place the Fe-Ni-Co-Cr-Mo high entropy alloy in a vacuum heat treatment furnace and heat it to 1200°C for 2 hours; the heating rate is 7°C / min; the vacuum degree in the vacuum heat treatment furnace is 1.0×10 -3 Pa;

[0056] 3: Cool the vacuum heat treatment furnace to 750°C and keep it for 6 hours; the cooling rate is 5°C / min.

[0057] 4: Cool the iron-nickel-cobalt-chromium-molybdenum high entropy alloy to room temperature and take it out from the vacuum heat treatment furnace.

[0058] Example 4

[0059] 1: Prepare a high entropy alloy; the high entropy alloy is prepared by a powder metallurgy method, especially an iron-nickel-cobalt-chromium-molybdenum high entropy alloy prepared by a hot isostatic pressing method; the purity of the iron-nickel-cobalt-chromium-molybdenum high entropy alloy is ≥99.5wt%; the iron-nickel-cobalt-chromium-molybdenum high entropy alloy is composed of Fe, Ni, Co, Cr, Mo, C, Si, Mn, and W elements, and the remainder is unavoidable impurity elements.

[0060] 2: Place the Fe-Ni-Co-Cr-Mo high entropy alloy in a vacuum heat treatment furnace and heat it to 1200°C for 3 hours; the heating rate is 7°C / min; the vacuum degree in the vacuum heat treatment furnace is 1.0×10 -3 Pa;

[0061] 3: Cool the vacuum heat treatment furnace to 850°C and keep it warm for 10 hours; the cooling rate is 5°C / min.

[0062] 4: Cool the iron-nickel-cobalt-chromium-molybdenum high entropy alloy to room temperature and take it out from the vacuum heat treatment furnace.

[0063] Table 1 Energy spectrum values ​​of the enhanced phase of the high entropy alloy prepared in Example 1 (wt%)

[0064] Spectrum C Si Cr Fe Co Ni Mn Mo W 1 0.45 1.05 20.45 18.73 21.06 23.63 0.6 12.93 1.10 2 0.44 1.10 19.56 20.17 21.89 22.96 0.8 12.08 1.0

[0065] pass Figure 3 It was calculated by using Pro Imaging software that the area ratio of the reinforcement phase in Example 1 is 40.11%. It can be seen from the energy spectrum value of the reinforcement phase corresponding to Example 1 in Table 1 that the reinforcement phase contains silicon, and the iron-nickel-cobalt-chromium-molybdenum high entropy alloy cooled to room temperature in step S104 of Example 1 is tested, and its elongation after fracture is 15% to 18%. Therefore, the elongation of the nickel-cobalt-chromium-molybdenum high entropy alloy is improved by the method for improving the elongation of the high entropy alloy of the present invention.

[0066] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like that may appear in the above description indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention.

[0067] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0068] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0069] In the embodiments of the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0070] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0071] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present invention are indicated by the appended claims.

Claims

1. A method for improving the elongation of a high entropy alloy, characterized in that: Follow the steps below to implement: Prepare a high entropy alloy, firstly place the high entropy alloy in a vacuum heat treatment furnace, raise the temperature to 1100° C.-1200° C., and keep the temperature for 2 hours-3 hours; secondly cool the vacuum heat treatment furnace to 750° C.-850° C., and keep the temperature for 6 hours-10 hours; finally cool the high entropy alloy to room temperature and take it out of the vacuum heat treatment furnace; Wherein, the high entropy alloy is an iron-nickel-cobalt-chromium-molybdenum series high entropy alloy; the high entropy alloy is prepared by hot isostatic pressing; the heating rate when the temperature in the vacuum heat treatment furnace is raised to 1100°C-1200°C is 7°C / min-10°C / min; The cooling rate when the temperature in the vacuum heat treatment furnace is reduced to 750°C-850°C is 3°C / min-5°C / min; The microstructure of the finally obtained iron-nickel-cobalt-chromium-molybdenum series high entropy alloy consists of a matrix phase and a reinforcement phase, the area ratio of the reinforcement phase is 40%-50%, and the elongation after fracture at room temperature is 15-18%.

2. The method for improving the elongation of a high entropy alloy according to claim 1, characterized in that: The high entropy alloy is prepared by a powder metallurgy method.

3. The method for improving the elongation of a high entropy alloy according to claim 1, characterized in that: The alloy purity of the iron-nickel-cobalt-chromium-molybdenum series high entropy alloy is ≥99.5wt%.

4. The method for improving the elongation of a high entropy alloy according to any one of claims 1 to 3, characterized in that: The vacuum degree in the vacuum heat treatment furnace is 1.0x10 -2 Pa~1.0x10 -3 Pa.

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