A high-entropy alloy with both room temperature and high temperature high strength and its preparation method and application

Abstract

The present invention discloses a high-entropy alloy that combines high strength at both room temperature and high temperature, as well as its preparation method and application, belonging to the field of alloy materials. The high-entropy alloy comprises, by weight percentage, 27.6-33.5% Ni, 27.0-33.0% Co, 20.5-26.5% Cr, 2.0-10.0% Fe, 3.2-5.6% Mo, 3.0-5.1% W, 0.5-2.4% Ti, 0.1-1.5% Al, 0.06-0.15% C, and 0.001-0.01% B, with the remainder being unavoidable impurities. The high-entropy alloy provided by the present invention exhibits ultrahigh yield strength at room temperature and excellent tensile strength and long life at temperatures up to 700°C. It also has a wide hot working window, exhibits no crack formation during forging and welding, and is therefore easy to process and apply.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of alloy materials, and specifically to a high-entropy alloy having high strength at room temperature and high temperature, and a preparation method and application thereof. Background Art

[0002] High-entropy alloys (HEAs), based on the concept of multi-principal element alloy design, break through the performance limits of traditional and existing materials and possess many outstanding properties, such as excellent high-temperature resistance, corrosion resistance, high strength, and wear resistance. Transition element HEAs utilize Al, Mg, Co, Cu, Cr, Fe, Mn, Ni, Ti, Sn, and Zn as their principal elements. AlCrFeNi, CoCrFeNi, AlCoFeNi, AlCoCrNi, and AlCoCrFe are the most commonly used element combinations in HEAs. Transition element HEAs are generally solid solution alloys with BCC or FCC structural phases. While single-phase HEAs exhibit excellent room-temperature mechanical properties, their high-temperature strength is unsatisfactory. Therefore, based on the precipitation-enhanced design method of traditional high-temperature alloys, the concept of HEAs has been proposed.

[0003] High-entropy superalloys are a class of high-entropy alloys with an FCC or BCC solid solution matrix and an ordered second phase with a similar crystal structure uniformly distributed throughout the matrix. This second phase acts as a precipitation strengthening agent. This high-entropy superalloy has a γ phase with a solid solution FCC structure as its matrix, with an L12-γ' precipitate uniformly distributed throughout the matrix. This γ' phase exhibits greater high-temperature stability than traditional Ni-Fe-based superalloys. This high-temperature stable precipitate can effectively enhance the room-temperature and high-temperature properties of high-entropy superalloys. Summary of the Invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0005] Advanced high-temperature structural materials, represented by superalloys and intermetallic compounds, are key materials used in the manufacture of hot-end components for aerospace and energy and power generation. As aerospace engines gradually develop towards larger sizes, higher thrust-to-weight ratios, and higher efficiency, the service temperatures and loads of hot-end components for advanced engines are required to continue to rise. This places ever-more stringent demands on the temperature-bearing capacity, performance, and specific gravity of the high-temperature structural materials themselves. However, the development of traditional high-temperature alloy systems has almost reached its limit. Traditional iron- and nickel-based superalloys, represented by GH4169 and GH2132, have low room-temperature yield strengths, and long-term operating temperatures are only below 600°C. Performance improvements are reaching a bottleneck, and are unable to meet the urgent demand for a new generation of high-temperature structural materials in this field. Therefore, it is necessary to develop a new generation of high-entropy alloy materials that combine high strength at both room temperature and high temperatures.

[0006] The present invention aims to solve one of the above-mentioned related technical problems to a certain extent. For this purpose, an embodiment of the present invention provides a high-entropy alloy that takes into account both room temperature and high-temperature high strength. This alloy not only has an ultra-high yield strength at room temperature, but also has relatively high strength and good creep properties at a high temperature of 700 °C. In terms of comprehensive performance, it has a higher service temperature, better oxidation resistance and corrosion resistance compared with the traditional nickel-based superalloy GH4169, higher strength compared with the cobalt-based superalloy GH605, and has significant advantages such as higher room-temperature yield strength, low cost, and easy processing and forming compared with GH350 and GH4141.

[0007] For the high-entropy alloy that takes into account both room temperature and high-temperature high strength provided by the present invention, by weight percentage, the composition of the high-entropy alloy is as follows: Ni: 27.6 - 33.5%, Co: 27.0 - 33.0%, Cr: 20.5 - 26.5%, Fe: 2.0 - 10.0%, Mo: 3.2 - 5.6%, W: 3.0 - 5.1%, Ti: 0.5 - 2.4%, Al: 0.1 - 1.5%, C: 0.06 - 0.15%, B: 0.001 - 0.01%, and the balance is inevitable impurities.

[0008] Advantages and technical effects brought by the high-entropy alloy that takes into account both room temperature and high-temperature high strength in the embodiment of the present invention:

[0009] 1. In the embodiment of the present invention, a four-principal-element system of Cr, Co, Ni, and Fe is adopted to maintain a high mixing entropy stable phase, which has a strong solid-solution strengthening effect; at the same time, W and Mo elements are further added. The alloying of large-atomic-radius added elements will introduce lattice distortion energy and form a lower atomic packing structure, thus forming a solid-solution structure such as a face-centered cubic (FCC) solid solution structure, playing a role in solid-solution strengthening and significantly improving the room-temperature yield strength of the alloy.

[0010] 2. In the embodiment of the present invention, by adding two γ'-phase forming elements, Al and Ti, a large number of nano-sized L12-γ' precipitates are formed on the matrix of the high-entropy alloy. The high-temperature stability of this γ' phase is better than that of traditional Ni-Fe-based superalloys. This high-temperature stable precipitate can effectively strengthen the high-temperature tensile strength of the high-entropy alloy, and the precipitation strengthening of the nano-precipitate (L12) is the main strengthening mechanism.

[0011] 3. In the embodiment of the present invention, non-metallic elements such as B and C are added. B and C have relatively small atomic radii and enter the alloy in the form of interstitial atoms. Severe lattice distortion hinders the movement of dislocations, thus playing a strengthening role, and both can promote the formation of the FCC phase in the alloy, thereby improving plasticity. The stably existing nano-sized γ' phase plays a role in precipitation strengthening. By reasonably matching grain boundary strengthening elements such as B and C, the high-temperature strength and creep properties of the alloy are significantly improved.

[0012] 4. In the embodiment of the present invention, the mass percentage of the elements Al, Ti, W and Mo in the high entropy alloy is limited to satisfy the relationship 0.2<(W+Mo) / [4*(Al+Ti)]<2.2. This is due to the "cocktail" effect on the performance of high entropy alloys, which makes the type, content and interaction of alloying elements affect the phase structure and performance of the alloy. When (W+Mo) / [4*(Al+Ti)]>2.2, too many large-sized solid solution strengthening elements affect the formation of precipitation phases, and as the Al content decreases, the shape of the precipitation phase changes significantly, causing the high-temperature mechanical properties to deteriorate. However, when (W+Mo) / [4*(Al+Ti)]<0.2, the thermal stability of the alloy is greatly deteriorated, and an ordered L12 precipitation phase is easily formed after long-term heat treatment, which significantly reduces the high-temperature endurance life.

[0013] 5. The high-entropy alloys of the present invention exhibit a wide thermal processing window, exhibit minimal surface cracking during forging, exhibit excellent plasticity, and achieve a high yield rate. They exhibit a yield strength exceeding 1200 MPa at room temperature and a lifespan exceeding 100 hours at 880°C / 100 MPa, meeting the design and operational requirements for hot-end components in advanced aircraft engines and gas turbines.

[0014] In some embodiments, the mass percentages of Al, Ti, W, and Mo satisfy the relationship 0.2 < (W + Mo) / [4 * (Al + Ti)] < 2.2. In some embodiments, the mass percentages of Al, Ti, W, and Mo satisfy the relationship 0.4 < (W + Mo) / [4 * (Al + Ti)] < 1.9.

[0015] In some embodiments, the impurities are Si≤0.20%, and / or Mn≤0.20%, and / or Cu≤0.20%, and / or P≤0.01%, and / or S≤0.01%, and / or Pb≤0.005%.

[0016] The embodiments of the present invention also provide the application of high entropy alloys that have both room temperature and high temperature high strength in aviation and aerospace engines.

[0017] The embodiments of the present invention also provide the application of high entropy alloys that have both room temperature and high temperature high strength in gas turbines.

[0018] The present invention also provides a method for preparing a high-entropy alloy having both room temperature and high temperature high strength, comprising the following steps:

[0019] Take the alloy raw materials, place them in a melting furnace with a vacuum degree of ≤5Pa according to the proportion, heat them to a molten state, continue to heat them to the refining temperature, keep them warm for refining, and vacuum cast them to obtain ingots;

[0020] The ingot is homogenized, and then finished, forged, and heat treated to obtain alloy bars; or the ingot is finished, hot rolled, annealed and softened, finished again, cold rolled, intermediate heat treated, and cold rolled to obtain alloy strips or foils;

[0021] The alloy rod, alloy strip or foil is heat-treated to form the high entropy alloy having both room temperature and high temperature high strength.

[0022] The advantages and technical effects brought about by the high-entropy alloy preparation method of the embodiment of the present invention are as follows: 1. In the embodiment of the present invention, the high-entropy alloy prepared by this preparation method has ultra-high mechanical strength at room temperature, with a yield strength of more than 1200MPa and an elongation of more than 15%. It also has excellent tensile strength and long-lasting life at a high temperature of 700°C, with a tensile strength of 936-1194MPa at 700°C. It also has a wide hot working window and does not crack during forging and welding, making it easy to process and apply. The excellent oxidation resistance, high-temperature tensile properties, long-lasting life, and low density, as well as the absence of cracks during forging, hot rolling, and cold rolling, meet the requirements of the design and use of advanced aviation, aerospace engines, and gas turbines. 2. In the embodiment of the present invention, the preparation process is simple, which reduces energy consumption, shortens the production cycle, and improves production efficiency, making it suitable for promotion and application in industrial production.

[0023] In some embodiments, the refining temperature is 1500-1650° C., and the refining time is 10-30 minutes.

[0024] In some embodiments, the homogenization treatment is performed at a temperature of 950 to 1200° C. for a time of 0.5 to 2 hours.

[0025] In some embodiments, the heat treatment is performed at a temperature of 700 to 900° C. for 5 to 20 hours. DETAILED DESCRIPTION

[0026] The following describes in detail embodiments of the present invention. The embodiments are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0027] The high-entropy alloy of the embodiment of the present invention, which takes into account both room temperature and high temperature high strength, is composed of, in terms of weight percentage, Ni: 27.6-33.5%, Co: 27.0-33.0%, Cr: 20.5-26.5%, Fe: 2.0-10.0%, Mo: 3.2-5.6%, W: 3.0-5.1%, Ti: 0.5-2.4%, Al: 0.1-1.5%, C: 0.06-0.15%, B: 0.001-0.01%, and the remainder is unavoidable impurities.

[0028] In some embodiments, preferably, the mass percentage contents of Al, Ti, W, and Mo satisfy the relational expression 0.2 < (W + Mo) / [4×(Al + Ti)] < 2.2.

[0029] In the embodiments of the present invention, by adding solid solution strengthening elements W and Mo, they can be dissolved not only in the alloy matrix but also in the γ' strengthening phase. At the same time, the atomic bonding force can be increased, the diffusion activation energy and the recrystallization temperature can be raised, thereby effectively improving the high-temperature strength. Al and Ti are the main elements for forming the γ' strengthening phase, which can greatly improve the precipitation strengthening effect of the alloy and enhance the high-temperature mechanical properties of the alloy. Due to the "cocktail" effect of the high-entropy alloy in terms of performance, the types, contents, and interactions of alloying elements will all affect the phase structure and properties of the alloy. Therefore, in order to maximize the synergistic effect of Al, W, Mo, and Ta, the mass percentage contents of Al, Ti, W, and Mo are further preferably such that they satisfy the relational expression 0.2 < (W + Mo) / [4×(Al + Ti)] < 2.2. This is because when (W + Mo) / [4×(Al + Ti)] < 0.2, the thermal stability of the alloy deteriorates extremely, and an ordered L12 precipitation phase is easily formed after long-term heat treatment, significantly reducing the high-temperature creep life. When (W + Mo) / [4×(Al + Ti)] > 2.2, excessive large-sized solid solution strengthening elements affect the formation of the precipitation phase, and with the decrease of the Al content, the shape of the precipitation phase changes significantly, deteriorating the high-temperature mechanical properties.

[0030] In some embodiments, preferably, the mass percentage contents of Al, Ti, W, and Mo elements in the high-entropy alloy that takes into account both room temperature and high-temperature high strength satisfy the relational expression 0.4 < (W + Mo) / [4×(Al + Ti)] < 1.9.

[0031] In some embodiments, preferably, the impurities are Si ≤ 0.20%, and / or Mn ≤ 0.20%, and / or Cu ≤ 0.20%, and / or P ≤ 0.01%, and / or S ≤ 0.01%, and / or Pb ≤ 0.005%.

[0032] The embodiments of the present invention also provide an application of the high-entropy alloy that takes into account both room temperature and high-temperature high strength in aviation and aerospace engines. The high-entropy alloy that takes into account both room temperature and high-temperature high strength in the embodiments of the present invention meets the requirements of advanced aviation and aerospace engine design and use, and can be applied to the hot-end components of advanced aviation and aerospace engines.

[0033] The embodiments of the present invention also provide an application of the high-entropy alloy that takes into account both room temperature and high-temperature high strength in gas turbines. The high-entropy alloy that takes into account both room temperature and high-temperature high strength in the embodiments of the present invention meets the requirements of advanced gas turbine design and use, and can be applied to the hot-end components of advanced gas turbines.

[0034] The present invention also provides a method for preparing a high-entropy alloy having both room temperature and high temperature high strength, the method comprising:

[0035] Take the alloy raw materials, place them in a melting furnace with a vacuum degree of ≤5Pa according to the proportion, heat them to a molten state, continue to heat them to the refining temperature, keep them warm for refining, and vacuum cast them to obtain ingots;

[0036] The ingot is homogenized, and then finished, forged, and heat treated to obtain alloy bars; or the ingot is finished, hot rolled, annealed and softened, finished again, cold rolled, intermediate heat treated, and cold rolled to obtain alloy strips or foils;

[0037] The alloy rod, alloy strip or foil is heat-treated to form the high entropy alloy having both room temperature and high temperature high strength.

[0038] The high-entropy alloy preparation method of the present invention provides a high-entropy alloy with ultra-high mechanical strength at room temperature, a yield strength exceeding 1200 MPa, an elongation exceeding 15%, and excellent tensile strength and longevity at 700°C. The tensile strength at 700°C is 936-1194 MPa, and the alloy exhibits a wide hot working window, exhibiting no crack formation during forging and welding, facilitating processing and application. The alloy's excellent oxidation resistance, high-temperature tensile properties, longevity, and low density, combined with the absence of crack formation during forging, hot rolling, and cold rolling, meet the design and use requirements of advanced aviation, aerospace engines, and gas turbines, making it suitable for widespread application in industrial production.

[0039] In some embodiments, preferably, the refining temperature is 1500-1650° C., and the refining time is 10-30 min.

[0040] In some embodiments, preferably, the homogenization treatment is performed at a temperature of 950 to 1200° C. for a time of 0.5 to 2 hours.

[0041] In some embodiments, preferably, the heat treatment temperature is 700-900° C., and the time is 5-20 h.

[0042] The present invention is described in detail below with reference to the embodiments.

[0043] Example 1

[0044] (1) The alloy raw materials were placed in a melting furnace with a vacuum degree of 0.2 Pa and heated to a molten state, and then the temperature was further raised to 1590°C and kept at this temperature for 20 minutes for refining, and vacuum casting was performed to obtain an ingot;

[0045] (2) homogenizing the ingot at 1180° C. for 1.5 h, followed by finishing, hot rolling, annealing and softening heat treatment, re-finishing, cold rolling, intermediate heat treatment, and cold rolling to obtain an alloy strip;

[0046] (3) The alloy strip is subjected to heat treatment at 820° C. for 20 h to form the high entropy alloy having both room temperature and high temperature high strength.

[0047] The composition of the alloy prepared in Example 1 is shown in Table 1, and the properties are shown in Table 2.

[0048] The preparation methods of Examples 2-8 are the same as those of Example 1, except that the alloy compositions are different. The compositions of the alloys prepared in Examples 2-8 are shown in Table 1, and the properties are shown in Table 2.

[0049] Comparative Example 1

[0050] The preparation method of Comparative Example 1 is the same as that of Example 1, except that the alloy composition does not contain Al and Ti elements. The composition of the alloy prepared in Comparative Example 1 is shown in Table 1, and the properties are shown in Table 2.

[0051] Comparative Example 2

[0052] The preparation method of Comparative Example 2 is the same as that of Example 1, except that the alloy composition does not contain C and B elements. The composition of the alloy prepared in Comparative Example 2 is shown in Table 1, and the properties are shown in Table 2.

[0053] Comparative Example 3

[0054] The preparation method of Comparative Example 3 is the same as that of Example 1, except that (W+Mo) / [4*(Al+Ti)]=0.1. The composition of the alloy prepared in Comparative Example 3 is shown in Table 1, and the properties are shown in Table 2.

[0055] Comparative Example 4

[0056] The preparation method of Comparative Example 4 is the same as that of Example 1, except that (W+Mo) / [4*(Al+Ti)]=2.9. The composition of the alloy prepared in Comparative Example 4 is shown in Table 1, and the properties are shown in Table 2.

[0057] Table 1 shows the alloy compositions of Examples 1-8 and Comparative Examples 1-4.

[0058] Table 1

[0059]

[0060]

[0061] Table 2 shows the alloy compositions of Examples 1-8 and the properties of the alloys of Comparative Examples 1-4.

[0062] Table 2

[0063]

[0064] As can be seen from the data in Table 1 and Table 2, in Examples 1-8 of the present invention, the contents of various elements in the alloy are all controlled within the range designed by the present invention. The high-entropy alloy obtained by adopting the preparation method of the present invention has a room-temperature yield strength of more than 1240 MPa, and a tensile strength at 700 °C of 936 MPa or more. Among them, the tensile strength at 700 °C of Examples 1, 2, 4, 6, and 8 exceeds 1040 MPa, indicating that the alloy has excellent mechanical strength at both room temperature and high temperature. In addition, the elongation after fracture of the alloy in Examples 1-8 at room temperature reaches more than 15%, showing good plasticity. The creep life of the alloy under the conditions of 880 °C and 100 MPa reaches more than 120 h, and the elongation after fracture exceeds 14%, with excellent comprehensive mechanical properties at high temperature. And the alloy has good workability, and no cracks are generated after forging and hot rolling.

[0065] In the alloy composition of Comparative Example 1, there are no Al and Ti elements, resulting in the inability to precipitate a large number of nano-sized L12-γ' precipitate phases in the alloy matrix. Therefore, the high-temperature tensile strength decreases significantly, and the tensile strength at 700 °C drops below 600 MPa. The creep life under the conditions of 880 °C and 100 MPa is only 34 h, which cannot meet the high-temperature use requirements of hot-end components of engines and gas turbines.

[0066] In the alloy composition of Comparative Example 2, there are no B and C elements, lacking the strengthening effect of interstitial atoms at the grain boundaries of the alloy. Although there are more W and Mo solid-solution strengthening elements in the alloy to keep the room-temperature tensile properties at a certain level, and the presence of Al and Ti elements makes the tensile strength of the alloy reach 985 MPa at 700 °C, the precipitation strengthening phase cannot maintain a stable state under a long-term high-temperature environment. Therefore, the creep life under the conditions of 880 °C and 100 MPa is only 62 h, and the elongation after fracture is less than 12%, with a significant decrease in high-temperature mechanical stability.

[0067] In the alloy composition of Comparative Example 3, there are excessive Al and Ti elements, the contents of W and Mo are lower than the range designed by the present invention, and the mass percentage contents of Al, Ti, W, and Mo do not satisfy the limiting relationship, (W + Mo) / [4*(Al + Ti)] = 0.1. This leads to extremely deteriorated thermal stability of the alloy, and an ordered L12 precipitate phase is formed after long-term heat treatment, significantly reducing the high-temperature creep life. And due to the significant decrease in the solid-solution strengthening ratio of W, Mo, etc., the room-temperature yield strength is significantly reduced to 1036 MPa. In addition, the imbalance in the alloy element ratio leads to cracks during hot rolling, the workability of the alloy is poor, and the comprehensive performance is poor, unable to meet the use requirements.

[0068] In Comparative Example 4, the mass percentage contents of Al, Ti, W, and Mo in the alloy composition do not satisfy the limiting relational expression, (W + Mo) / [4*(Al + Ti)] = 2.9. Excessive large-sized solid solution strengthening elements affect the formation of the precipitation phase, resulting in a high-temperature tensile strength of only 688 MPa at 700 °C, and the creep properties deteriorate significantly, unable to meet the usage requirements.

[0069] Although the present invention has been described in detail with general descriptions and specific embodiments above, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A high entropy alloy that has both room temperature and high temperature high strength, characterized in that: The high-entropy alloy comprises, in percentage by weight, 27.6-33.5% Ni, 27.0-33.0% Co, 20.5-26.5% Cr, 2.0-10.0% Fe, 3.2-5.6% Mo, 3.0-5.1% W, 0.5-2.4% Ti, 0.1-1.5% Al, 0.06-0.15% C, and 0.001-0.01% B, with the remainder being unavoidable impurities. The weight percentages of Al, Ti, W, and Mo satisfy the relationship 0.4<(W+Mo) / [4*(Al+Ti)]<2.

2. The room-temperature yield strength of the high-entropy alloy reaches above 1240 MPa, the tensile strength at 700°C reaches above 936 MPa, the endurance life at 880°C and 100 MPa reaches above 120 h, and the elongation after fracture exceeds 14%.

2. The high-entropy alloy that takes both room temperature and high-temperature high strength into account as described in claim 1, wherein The weight percentages of Al, Ti, W and Mo satisfy the relationship 0.4<(W+Mo) / [4*(Al+Ti)]<1.

9.

3. The high-entropy alloy that takes both room temperature and high-temperature high strength into account as claimed in claim 1, wherein The impurities are Si≤0.20%, and / or Mn≤0.20%, and / or Cu≤0.20%, and / or P≤0.01%, and / or S≤0.01%, and / or Pb≤0.005%.

4. Use of the high entropy alloy according to any one of claims 1 to 3, which has both room temperature and high temperature high strength, in aviation or aerospace engines.

5. Use of the high entropy alloy according to any one of claims 1 to 3, which has both high strength at room temperature and high temperature, in a gas turbine.

6. A method for preparing a high entropy alloy having both room temperature and high temperature high strength according to any one of claims 1 to 3, characterized in that: The method comprises: Take the alloy raw materials, place them in a melting furnace with a vacuum degree of ≤5Pa according to the proportion, heat them to a molten state, continue to heat them to the refining temperature, keep them warm for refining, and vacuum cast them to obtain ingots; The ingot is homogenized, and then subjected to finishing, hot rolling, annealing and softening heat treatment, re-finishing, cold rolling, intermediate heat treatment, and cold rolling to obtain an alloy strip or foil; The alloy strip or foil is heat-treated to form the high entropy alloy having both room temperature and high temperature high strength.

7. The preparation method of the high-entropy alloy that takes into account high strength at room temperature and high temperature according to claim 6, characterized in that, The refining temperature is 1500-1650° C., and the refining time is 10-30 minutes.

8. The preparation method of the high-entropy alloy that takes into account high strength at room temperature and high temperature according to claim 6, characterized in that, The homogenization treatment is carried out at a temperature of 950-1200° C. and for a time of 0.5-2 h.

9. The method for preparing a high-entropy alloy having both room temperature and high temperature high strength according to claim 6, characterized in that: The heat treatment temperature is 700-900° C. and the time is 5-20 hours.

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