Novel tough light-weight high-temperature medium-entropy alloy and preparation process thereof

Abstract

The invention discloses a novel tough light-weight high-temperature medium-entropy alloy and a preparation process thereof, and relates to the technical field of alloy preparation. The tough light-weight high-temperature medium-entropy alloy comprises the following elements in percentage by mole: 45 to 50 percent of Ti, 15 to 25 percent of Al, 15 to 25 percent of Nb, 3 to 5 percent of Ta, 3 to 5 percent of V, 0.1 to 0.5 percent of Si and 0.05 to 0.2 percent of B. The novel tough light-weight high-temperature medium-entropy alloy has the characteristics of low density (approximately equal to 5.6 g / cm < 3 >), high-temperature high-strength (yield strength at 650 DEG C is greater than or equal to 965 MPa) and low cost, and overcomes the core technical bottlenecks of high density, unstable high-temperature performance, high cost and the like of the traditional refractory alloy; and a high-cost-performance solution with excellent performance and economical efficiency is provided for structural materials in the fields of aerospace, extreme high-temperature equipment and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy preparation, and particularly to a new type of ductile lightweight high-temperature medium-entropy alloy and its preparation process. Background Art

[0002] As engineering structural materials, metallic materials are widely used in all walks of life in society. With the rapid development of technology, the industrial sector's demand for metallic materials is continuously increasing, requiring them to possess more excellent properties, higher reliability, and more competitive costs. However, traditional alloys are restricted by a single main element and are difficult to meet the increasingly demanding usage requirements, thus making the available high-performance materials more limited and restricting the diversity and development potential of alloy properties to a certain extent. The concept of medium- and high-entropy alloys breaks the limitation of the single-principal-element design of traditional alloys and has a wider composition design space. Medium-entropy alloys exhibit many advantages in terms of performance, including high strength, high hardness, wear and corrosion resistance, and good thermal stability, etc.

[0003] Refractory medium-entropy alloys have characteristics such as high melting points, high hardness, and excellent high-temperature strength, combining the advantages of medium-entropy alloys and refractory metals. These alloys exhibit excellent mechanical properties and anti-softening properties at high temperatures and thus have important application significance in the field of extreme high temperatures. In contrast, the performance of traditional alloys (such as aluminum alloys and titanium alloys) at high temperatures is often affected by their own melting point limitations, phase changes, and grain coarsening, resulting in a decrease in strength and an increase in brittleness. Under extreme high-temperature conditions, the tensile properties of traditional alloys are generally inferior to those of refractory medium-entropy alloys. The higher melting points of refractory medium-entropy alloys make them ideal materials for future extreme high-temperature components. However, under high-temperature or specific environments, these alloys may undergo phase separation or form unstable phases, thus affecting their mechanical properties. In addition, the density of refractory medium-entropy alloys is relatively high, usually between 8 g / cm 3 and 12 g / cm 3 . This is because their main components are metal elements with relatively large densities, such as tungsten (W), molybdenum (Mo), and niobium (Nb), etc. For example, alloys such as VNbMoTaW and MoNbTaW have a density of approximately 10 g / cm 3 . Since the constituent elements such as hafnium (Hf), tantalum (Ta), and niobium (Nb), etc. are relatively expensive, economy is also an important factor restricting their application.

[0004] Regarding the problems faced by refractory medium-entropy alloys, some researchers have attempted to modify the alloys by adding light elements such as aluminum (Al), magnesium (Mg), silicon (Si), etc. Although this method has achieved certain results in reducing density and cost, the mechanical properties of the alloys may decrease significantly. Therefore, despite some progress in the development of refractory medium-entropy alloys, there are still some relatively intractable challenges. Currently, there is an urgent need to develop refractory medium-entropy alloys with excellent mechanical properties at high temperatures, while having relatively low density and cost. Summary of the Invention

[0005] The purpose of the present invention is to provide a novel ductile lightweight high-temperature medium-entropy alloy and its preparation process to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] The present invention provides a ductile lightweight high-temperature medium-entropy alloy, and the molar percentage content of the elements of the alloy is as follows:

[0008] Ti 45-50%, Al 15-25%, Nb 15-25%, Ta 3-5%, V 3-5%, Si 0.1-0.5% and B 0.05-0.2%.

[0009] Titanium alloys have the characteristics of high strength-to-weight ratio, good corrosion resistance, strong creep resistance, good fracture toughness, etc., and are widely used in the fields of aerospace, machinery, energy, etc. Among them, due to the good thermal stability and thermal strength of titanium alloys, they have more significant advantages than nickel-based superalloys, high-strength steels, aluminum-magnesium and other light alloys.

[0010] The novel ductile lightweight high-temperature medium-entropy alloy prepared by the present invention realizes the optimization and breakthrough of performance through the synergistic effect of seven elements, namely Ti, V, Al, Nb, Ta, Si, and B. Among them, the Al element, as a key strengthening component, significantly improves the strength and heat resistance of the alloy by virtue of its solid solution strengthening effect in the titanium matrix, enhancing both the tensile strength and yield strength of the alloy. β-stabilizing elements such as V, Nb, and Ta are incorporated into the β-titanium alloy lattice in the form of substitutional solid solution, maximizing the retention of plasticity while effectively improving the strength of the alloy. The V element can inhibit the harmful eutectoid reaction in the titanium alloy and enhance the tissue stability; the Nb element can enhance the oxidation resistance of the alloy, significantly improve the high-temperature strength and creep resistance, ensuring that the alloy still maintains excellent mechanical properties in a high-temperature environment; the Ta element focuses on improving the oxidation and corrosion resistance of the alloy, further expanding the application scenarios of the alloy. The Si element effectively strengthens the alloy matrix through the dual mechanisms of solid solution strengthening and silicide precipitation strengthening, significantly improving its high-temperature performance. The B element, as an efficient grain refiner, effectively inhibits grain growth during solidification by forming borides, refining the microstructure, and thus further enhancing the strength of the alloy. The present invention uses a variety of elements in combination to endow the alloy with excellent comprehensive properties, showing great application potential in the field of high-temperature structural materials.

[0011] The present invention also provides a preparation method for the above-mentioned ductile lightweight high-temperature medium-entropy alloy, including the following steps:

[0012] (1) According to the element ratio of the ductile lightweight high-temperature medium-entropy alloy, melt the raw materials;

[0013] (2) Cool the alloy in a molten state obtained in step (1);

[0014] (3) Homogenize the alloy billet obtained in step (2) at a first preset temperature for a first preset duration;

[0015] (4) Perform cold rolling on the alloy processed in step (3) to obtain the ductile lightweight high-temperature medium-entropy alloy.

[0016] As a further preference of the present invention, the molar percentage content of alloy elements is as follows:

[0017] Ti 49.4%, Al 20%, Nb 20%, Ta 5%, V 5%, Si 0.5%, and B 0.1%.

[0018] As a further preference of the present invention, step (2) is: using the copper mold suction casting method to process the alloy in a molten state to obtain an alloy billet; specifically, sucking the alloy in a molten state into a plate-shaped water-cooled copper mold to obtain an alloy billet;

[0019] As a further preference of the present invention, the first preset temperature is 800 °C and the first preset duration is 1 h.

[0020] As a further preference of the present invention, step (1) is carried out in an argon atmosphere for smelting; the smelting adopts vacuum arc melting; the current of the vacuum arc melting is 60 - 80 A.

[0021] As a further preference of the present invention, the cold rolling treatment in step (4) is N passes, where 2 ≤ N ≤ 5.

[0022] The present invention discloses the following technical effects:

[0023] The present invention provides a new medium entropy alloy with low density (≈5.6 g / cm 3 ), high strength at high temperature (yield strength ≥ 965 MPa at 650 °C), and low cost, overcoming the core technical bottlenecks of traditional refractory alloys such as high density, unstable high-temperature performance, and high cost, and providing a cost-effective solution with excellent performance and economy for structural materials in fields such as aerospace and extreme high-temperature equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 X-ray diffraction analysis of the alloy materials prepared in Comparative Example 2 and Example 1 of the present invention (the abscissa is the 2θ angle; the ordinate is the intensity after normalization);

[0026] Figure 2 Microstructure morphology of the alloy materials prepared in Comparative Example 2 and Example 1 of the present invention;

[0027] Figure 3 Tensile property curves of the alloy materials in Example 1, Comparative Example 1, and Comparative Example 2 at 650 °C. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0029] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0030] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0031] Without departing from the scope or spirit of the present invention, various improvements and modifications can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0032] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0033] It should be noted that those aspects not detailedly described in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0034] The present invention will be described in detail below in conjunction with embodiments:

[0035] Example 1

[0036] Table 1

[0037]

[0038] Preparation of ductile lightweight high-temperature medium-entropy alloy:

[0039] (1) Weighing of raw materials and calculation of proportion

[0040] According to the alloy composition set in Table 1, accurately calculate the atomic percentage and mass percentage of each element, and measure the theoretical density of the alloy through the mixing rule to ensure that the composition ratio meets the design requirements.

[0041] (2) Pretreatment of raw materials

[0042] Select elemental raw materials with a purity of ≥99.9%, remove impurities such as surface oxide scales, and then ultrasonically clean with acetone and dry. Weigh the raw materials according to the ratio using a balance with a precision of 0.001 g to ensure the accuracy of measurement.

[0043] (3) Vacuum arc melting

[0044] Load the pretreated raw materials into a water-cooled non-consumable vacuum arc melting furnace in the order of "lowest melting point to highest melting point, smallest size to largest size". Evacuate to below 0.005 Pa and flush the furnace chamber with high-purity argon 3 times. Start the arc under argon protection, with an initial current of 60 A, and gradually increase it to 150 A to melt the titanium ingot. Then move the arc to other raw materials and melt them successively along the water-cooled copper crucible. Increase the current to 200 A and hold for 10 seconds to form a button-shaped alloy ingot. After repeating the melting 2 times, turn on the electromagnetic stirring function for the 3rd melting to promote the uniform diffusion of refractory components. After turning off the stirring, melt 2 more times, with a total of 5 meltings to ensure full homogenization of the composition.

[0045] (4) Copper mold suction casting

[0046] Keep the homogenized alloy melt at 300 A arc for 10 seconds. After the melt is completely molten, suck it into a customized plate-shaped water-cooled copper mold (width 10 mm × thickness 3 mm × height 80 mm) through negative pressure, and quickly cool to obtain a plate-shaped alloy blank with a thickness of 3 mm.

[0047] (5) Homogenization treatment

[0048] Place the alloy blank in a heat treatment furnace with a vacuum degree <0.005 Pa, hold at 800 °C for 1 hour to eliminate composition segregation; then air-cool to room temperature to obtain an alloy matrix with uniform structure.

[0049] (6) Cold rolling treatment: In the example, the alloy blank after homogenization treatment was cold-rolled in 5 passes successively. The reduction per pass was controlled at 20% of the alloy thickness of the previous pass.

[0050] Comparative example 1

[0051] The difference from Example 1 is only that the alloy composition is Ti-6Al-4V.

[0052] Comparative example 2

[0053] The difference from Example 1 is only that it is Ti50Al20Nb20Ta5V5.

[0054] Comparative example 3

[0055] The difference from Example 1 is only that it is Ti6Al2.7Sn4Zr0.4Mo0.45Si.

[0056] Comparative example 4

[0057] It is only different from Example 1 in that Ti5.8Al4.8Sn2Zr1Mo0.35Si0.85Nd.

[0058] Comparative Example 5

[0059] It is only different from Example 1 in that Ti6Al2.8Sn4Zr0.5Mo0.4Si0.1Y.

[0060] Comparative Example 6

[0061] It is only different from Example 1 in that Ti5.8Al4.0Sn4.0Zr0.4Si0.7Nb1.5Ta0.06C.

[0062] The crystal structure of the alloy was characterized by X-ray diffraction with a scanning angle of 10 - 90° and a scanning speed of 4° / min. Figure 1 It is the X-ray diffraction pattern of the alloy materials of Comparative Example 2 and Example 1. Figure 1 It shows that the phase composition of the novel medium-entropy alloy of the present invention is mainly the BCC structure phase, and the second phase B2 appears after adding element B and element Si.

[0063] The alloy materials prepared in Comparative Example 2 and Example 1 were subjected to microstructural characterization: The microstructures of the alloys were analyzed by using the BSE mode analysis of SEM with Zeiss Gemini 300. Figure 2 It reflects the influence of the addition or not of element B and element Si on the microstructure of the alloy. It can be seen that a large number of second-phase B2 appear in the alloy after adding element B and element Si. Combining Figure 3 with the tensile properties of the alloy in

[0064] The ductile lightweight high-temperature medium-entropy alloy was wire-cut to obtain tensile specimens for tensile mechanical testing:

[0065] The tensile test was completed on an MTS-CMT5205 universal mechanical testing machine. The gauge length of the tensile specimen was 12.7 mm, the gauge length of the extensometer was 12 mm, and the strain rate was 0.001 s -1 , and the tensile test was carried out at 650 °C.

[0066] The tensile test results of the alloy materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 are as Figure 3。The yield strength of the alloy material prepared in Comparative Example 2 was 556 GPa, the tensile strength was 638 MPa, and the tensile strain was 11%; the yield strength of the alloy material prepared in Example 1 reached 965 MPa, the tensile strength was as high as 1041 MPa, and the tensile strain was 6%. Although the plasticity decreased slightly, the strength increased significantly.

[0067] The mechanical properties of the alloy materials prepared in Example 1 and Comparative Examples 1-6 are shown in Table 2.

[0068] Table 2

[0069]

[0070] It can be seen that the alloy materials prepared by the present invention have excellent mechanical properties at high temperatures.

[0071] Based on the elements of Ti, Al, Nb, V, Ta, B, and Si, the present invention successfully prepared a series of novel refractory lightweight medium-entropy alloys by precisely controlling the element ratio and combining treatment processes such as cold rolling. This series of alloys combines high temperature high strength and good plasticity. Not only is the density significantly reduced, but the manufacturing cost is also greatly reduced, effectively overcoming the technical bottlenecks of traditional refractory medium-entropy alloys such as fluctuating high temperature performance, large density, and high cost, and providing an innovative solution with excellent performance and economic value for the field of high temperature structural materials.

[0072] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A tough, lightweight, high-temperature medium-entropy alloy, characterized in that: The molar percentages of alloying elements are as follows: Ti 45-50%, Al 15-25%, Nb 15-25%, Ta 3-5%, V 3-5%, Si 0.1-0.5% and B 0.05-0.2%.

2. The method for preparing a tough, lightweight, high-temperature medium-entropy alloy according to claim 1, characterized in that: The following steps are involved: (1) melting raw materials according to the element ratio of the tough, lightweight, high-temperature medium-entropy alloy; (2) cooling the molten alloy obtained in step (1); (3) homogenizing the alloy blank obtained in step (2) at a first preset temperature for a first preset time; (4) cold rolling the alloy after treatment in step (3) to obtain the tough, lightweight, high-temperature medium-entropy alloy.

3. The method for preparing a tough, lightweight, high-temperature medium-entropy alloy according to claim 2, characterized in that: The molar percentages of alloying elements are as follows: Ti 49.4%, Al 20%, Nb 20%, Ta 5%, V 5%, Si 0.5% and B 0.1%.

4. The method for preparing a tough, lightweight, high-temperature medium-entropy alloy according to claim 2, characterized in that: Step (2) is: using a copper mold suction casting method to process the molten alloy to obtain an alloy blank.

5. The method for preparing a tough, lightweight, high-temperature medium-entropy alloy according to claim 2, characterized in that: The first preset temperature is 800° C., and the first preset time is 1 hour.

6. The method for preparing a tough, lightweight, high-temperature medium-entropy alloy according to claim 2, characterized in that: Step (1) is to carry out smelting in an argon atmosphere.

7. The method for preparing a tough, lightweight, high-temperature medium-entropy alloy according to claim 2, characterized in that: The smelting adopts vacuum arc melting; the current of the vacuum arc melting is 60-80A.

8. The method for preparing a tough, lightweight, high-temperature medium-entropy alloy according to claim 2, characterized in that: The cold rolling process in step (4) is performed for N passes, 2≤N≤5.

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