A bcc structured refractory high-entropy alloy TiZrNbMoW with excellent dynamic mechanical properties
By forming an endogenous coherent dispersion of micron-sized W-rich phases in the TiZrNb alloy matrix, the problem of insufficient dynamic strength and ductility of high-entropy alloys during dynamic loading was solved, realizing a high-strength, high-ductility refractory high-entropy alloy suitable for extreme service environments.
Patent Information
- Application Number
- CN202310649785.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-02
- Publication Date
- 2025-11-21
- Estimated Expiration
- 2043-06-02
AI Technical Summary
Existing high-entropy alloys lack dynamic strength and ductility during dynamic loading. In particular, the CoCrNiMnFe series face-centered cubic and TiZrHfNbTa series body-centered cubic high-entropy alloys have failed to reach the ultimate strength of 2GPa. Furthermore, BMGCs and WHAs are prone to peeling and breakage during dynamic deformation, resulting in poor dynamic ductility.
By exploiting the differences in atomic size and modulus between Ti/Zr/Nb and W/Mo, and employing arc melting and water-cooled copper crucible rapid solidification techniques, an endogenous coherent dispersion of micron-sized W-rich phases is formed in the TiZrNb alloy matrix. This results in a TiZrNbMoW refractory high-entropy alloy with a two-body-centered cubic structure, which suppresses the formation of long-range adiabatic shear bands and deflects microcracks at high frequencies.
It significantly improves the dynamic compressive strength of the alloy to 2.1–2.6 GPa and the dynamic compressive plasticity to 30%, which is much higher than BMGCs and WHAs. Moreover, the preparation process is simple and low-cost, making it suitable for extreme service environments.
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Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of metal materials, in particular to a dual-body-centered cubic structure TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties, including microstructure characteristics, mechanical properties, toughening mechanisms and a preparation method thereof. BACKGROUND
[0002] Due to unique physical properties, high-entropy alloys exhibit excellent low-temperature toughness, high-temperature softening resistance and radiation damage resistance as structural materials under extreme conditions, showing attractive application prospects. This also prompts researchers to continuously explore the application of high-entropy alloys under extreme environments, such as dynamic mechanical properties, i.e. armor or penetration ability. However, neither the face-centered cubic high-entropy alloy of the CoCrNiMnFe series nor the body-centered cubic high-entropy alloy of the TiZrHfNbTa series has obtained satisfactory dynamic mechanical properties. So far, compared with the dynamic softening of bulk metallic glass composites (BMGCs) and tungsten heavy alloys (WHAs), high-entropy alloys have shown excellent dynamic ductility. However, the ultimate strength thereof fails to reach 2 GPa, which is far lower than that of BMGCs and WHAs, and has no obvious advantage compared with traditional materials such as steel or titanium alloy.
[0003] For BMGCs and WHAs, the dynamic strength thereof is usually improved by adding W fibers or endogenous precipitates. However, these structural characteristics also magnify the weakness thereof, i.e. the interfacial bonding force between the reinforcing phase and the matrix is seriously weakened, which makes the BMGCs and WHAs prone to be peeled and broken between the two phases during dynamic deformation. In addition, the BMGCs and WHAs are prone to generate adiabatic shear bands (ASBs), resulting in poor dynamic ductility. As known from the above, the strengthening of hard precipitates and the interfacial bonding force are important factors for determining the optimization of dynamic strength-ductility of alloys. The high-entropy alloy with a supersaturation feature provides a suitable model for the strategy of optimizing the dynamic strength and ductility of alloys by introducing endogenous coherent hard precipitates. This strategy not only maximizes the solid solution strengthening effect, but also introduces coherent hard precipitates with large modulus difference, further improving the dynamic strength of high-entropy alloys. At the same time, since the hard precipitates are in-situ coherent precipitates, the coherent interface feature ensures the interfacial bonding force between the two phases in the high-entropy alloy, inhibiting the peeling and breaking of the alloy between the two phases during dynamic deformation, which may have an unexpected toughening effect.
[0004] Therefore, we try to use the difference between the atomic size and modulus of Ti / Zr / Nb and W / Mo to realize in-situ supersaturation precipitation of hard phase in refractory high-entropy alloy, and since the alloy crystal structure composed of the above five components can only be body-centered cubic at room temperature, which ensures the coherency of the hard precipitated phase and the matrix. Currently, there is an urgent need for high-strength, high-plasticity metal functional materials in some extreme service environment fields. The refractory high-entropy alloy with endogenous coherent hard phase dispersion strengthening has wide application potential in these extreme service environment fields due to its simple preparation process, low preparation cost and excellent dynamic strength and plasticity, and has important significance for national defense security and industrial application. SUMMARY
[0005] The main purpose of the present application is to develop a bcc structure TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties, and the technical problem to be solved is to significantly improve the dynamic strength of the alloy while obtaining excellent dynamic ductility by the dispersion precipitation of endogenous coherent hard phase, and to avoid dynamic strain softening, so that the refractory high-entropy alloy has higher application value in dynamic loading and other extreme service environments.
[0006] The purpose of the present application and the technical problems thereof are realized by adopting the following technical scheme:
[0007] A bcc structure TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties, which has the following microstructure characteristics:
[0008] (1) The microstructure is that the micron-sized W-rich phase with bcc structure is dispersedly distributed in the bcc refractory high-entropy alloy matrix.
[0009] (2) The W-rich phase is a stable bcc structure in-situ precipitated in the matrix due to the supersaturation solid solution characteristics of the high-entropy alloy, and the volume fraction of the W-rich phase is in the range of 30% to 80%.
[0010] The bcc structure TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties has a room temperature yield strength of 1400-1600 MPa, an ultimate strength of 2100-2600 MPa, and a uniform elongation of 20-40% in the range of 1000 s -1 to 6000 s -1 dynamic loading speed.
[0011] The bcc structure TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties contains, in atomic percentage, 25-40% of Ti, 25-40% of Zr, 15-30% of Nb, and 15-30% of Mo and W.
[0012] The bcc structure TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties, and the preparation method of the refractory high-entropy alloy is as follows: arc melting a master alloy ingot, and rapidly solidifying the ingot by using a water-cooled copper crucible.
[0013] The bcc structure TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties, and the dynamic deformation characteristics and mechanism of the alloy are as follows:
[0014] (1) In the dynamic compression process, the alloy as a whole shows shear deformation, and shows good self-sharpening effect, but the alloy still maintains the sustained strain hardening capacity;
[0015] (2) The strain hardening capacity of the alloy mainly comes from two aspects: one is that the micron-sized W-rich phase dispersedly distributed inhibits the formation of long-range adiabatic shear bands, and makes the micro-cracks generated in the deformation process deflect at a high frequency, thereby promoting the dissipation of plastic work in the dynamic deformation process; and the other is that the micro-crack tip is pinned in the interior of the W-rich phase, resulting in an interface bridging effect, which inhibits the continuous expansion of the micro-crack, thereby enhancing the toughness of the refractory high-entropy alloy.
[0016] The design idea of the present application is as follows:
[0017] By Mo / W in-situ alloying, the present application forms micron-sized coherently distributed W-rich phases in the TiZrNb alloy matrix by using the water-cooled copper crucible rapid solidification technology, thereby forming a refractory high-entropy alloy with a bcc structure; the hardness and modulus of the W-rich phase are much higher than those of the matrix, the long-range adiabatic shear bands generated in the dynamic impact process are inhibited, and the micro-cracks generated are deflected and pinned at a high frequency by the W-rich phase, which effectively dissipates the plastic work in the dynamic loading process, thereby endowing the TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties.
[0018] By the above technical solution, the present application has the following advantages and beneficial effects:
[0019] 1、Currently, there is an urgent need for high-strength and high-ductility metal functional materials in some extreme service environment fields. By in-situ alloying of Mo / W, micron-sized coherent W-rich phases are formed in the TiZrNb alloy matrix by using rapid solidification technology. The difference in hardness and modulus between the W-rich phase and the matrix suppresses the formation of long-range adiabatic shear bands during dynamic impact, deflects the micro-crack propagation direction at high frequency, effectively pins the micro-crack tip, effectively dissipates the plastic work during dynamic loading, and endows the refractory high-entropy alloy with excellent dynamic mechanical properties. The dynamic compression ultimate strength of the refractory high-entropy alloy is 2.1-2.6 GPa, which is at the same level as that of traditional BMGCs and WHAs; the dynamic compression plasticity can reach 30%, which is much higher than that of BMGCs and WHAs. At the same time, the preparation process of the refractory high-entropy alloy is simple, the preparation cost is low, and it has wide application potential in extreme service environment fields, which has important significance for national defense security and industrial application.
[0020] 2、The present application proposes the concept of endogenous coherent dispersion strengthening high-entropy alloy, which significantly improves the dynamic mechanical properties of refractory high-entropy alloy, and the preparation process is simple and efficient, which makes it have outstanding application value in the field of national defense and military armor materials.
[0021] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, and can be implemented according to the content of the specification, the following will be described in detail with the preferred embodiments of the present application and with the help of the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 The as-cast XRD pattern of TiZrNbMo 0.3 W 0.3 alloy.
[0023] Figure 2 The as-cast SEM pattern of TiZrNbMo 0.3 W 0.3 alloy.
[0024] Figure 3 The compression true stress-strain diagram of as-cast TiZrNbMo 0.3 W 0.3 alloy at different strain rates.
[0025] Figure 4 The SEM pattern of the deformation characteristics near the fracture of TiZrNbMo 0.3 W 0.3 alloy after dynamic compression at 3735 s -1 strain rate. DETAILED DESCRIPTION
[0026] In the specific implementation process, the TiZrNbMoW refractory high-entropy alloy with the dual body-centered cubic structure and excellent dynamic mechanical properties has the following specific preparation techniques, micro characteristics, mechanical properties and deformation mechanisms:
[0027] 1. A TiZrNbMoW refractory high-entropy alloy with a dual body-centered cubic structure and excellent dynamic mechanical properties, and a preparation method thereof is described as follows:
[0028] First, the atomic ratio of each element in the TiZrNbMoW alloy is determined, and the alloy is prepared according to the proportioning. Ti / Zr intermediate alloy ingots and Nb / Mo / W intermediate alloy ingots are prepared by melting, and then the two kinds of intermediate alloy ingots are put into the same crucible to prepare the master alloy ingot. The master alloy ingot is heated and melted by arc melting, and is repeatedly melted for 4-6 times until the composition is uniform. Low current melting is used for the last time, and water-cooled copper crucible is used for rapid cooling and solidification, so as to obtain the TiZrNbMoW refractory high-entropy alloy. The specific process is as follows:
[0029] (1) Preparation of Ti / Zr intermediate alloy ingot: according to the preset component proportioning, the titanium raw material and the zirconium raw material are weighed and placed in the crucible. When arc melting is used, the vacuum chamber is first pre-extracted to 10 -4 ~10 -3 Pa, and then high-purity argon gas (volume purity 99.999%) is filled until the vacuum gauge shows 4×10 4 ~8×10 4 Pa. The alloy melting current is 200-350 A, each melting time is 1-2 minutes, and the alloy is turned over for re-melting after each melting, which is repeated at least 3 times until the alloy composition is uniform, and the Ti / Zr intermediate alloy ingot is obtained.
[0030] (2) Preparation of Nb / Mo / W intermediate alloy ingot: according to the preset component proportioning, the niobium raw material, the molybdenum raw material and the tungsten raw material are weighed and placed in the crucible. When arc melting is used, the vacuum chamber is first pre-extracted to 10 -4 ~10 -3 Pa, and then high-purity argon gas (volume purity 99.999%) is filled until the vacuum gauge shows 4×10 4 ~8×10 4 Pa. The alloy melting current is 400-600 A, each melting time is 1-2 minutes, and the alloy is turned over for re-melting after each melting, which is repeated at least 5 times until the alloy composition is uniform, and the Ti / Zr intermediate alloy ingot is obtained.
[0031] (3) Preparation of master alloy ingot: the Ti / Zr intermediate alloy ingot and the Nb / Mo / W intermediate alloy ingot are mixed and melted, the alloy melting current is 400-500 A, each melting time is 1-2 minutes, and the alloy is turned over for re-melting after each melting, which is repeatedly melted until the composition is uniform, and the master alloy ingot is obtained.
[0032] 2. A bcc structured TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties, having the following composition and microstructure characteristics:
[0033] (1) In the TiZrNbMoW refractory high-entropy alloy, the atomic percentage of Ti is 25-40%, the atomic percentage of Zr is 25-40%, the atomic percentage of Nb is 15-30%, and the sum of the atomic percentages of Mo and W is 15-30%.
[0034] (2) The as-cast microstructure is a micron-sized W-rich phase with a bcc structure that is endogenous and coherent with the matrix, and is dispersed in the bcc refractory high-entropy alloy matrix.
[0035] (3) The W-rich phase is a stable bcc structure that is in-situ precipitated in the matrix due to the supersaturated solid solution characteristics of the high-entropy alloy, and the volume fraction of the W-rich phase is in the range of 30-80%.
[0036] 3. A bcc structured TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties, having the following mechanical properties at different compression rates:
[0037] At 1000 s -1 - 6000 s -1 In the dynamic loading speed range, the yield strength of the alloy at room temperature is 1400-1600 MPa, the ultimate strength is 2000-2600 MPa, and the uniform elongation is 20-40%.
[0038] 4. A bcc structured TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties, having the following dynamic deformation characteristics and mechanisms:
[0039] (1) During dynamic compression, the alloy as a whole exhibits shear deformation, showing good self-sharpening effect, but the alloy also maintains sustained strain hardening ability.
[0040] (2) The strain hardening ability of the alloy mainly comes from two aspects: first, the micron-sized W-rich phase dispersedly distributed can inhibit the formation of long-range adiabatic shear bands, and the microcracks generated during deformation can be deflected at a high frequency, thereby promoting the dissipation of plastic work during dynamic deformation; second, the microcrack tip can be pinned inside the W-rich phase, resulting in interface bridging effect, which inhibits the continuous expansion of the microcrack, thereby enhancing the toughness of the refractory high-entropy alloy.
[0041] In the following, the microstructure characteristics, mechanical properties and deformation mechanisms of the bcc structured TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties in the present application will be described in detail in conjunction with the accompanying drawings and specific examples.
[0042] Embodiment
[0043] One embodiment of the present application proposes a TiZrNbMo 0.3 W 0.3 The preparation method of the refractory high-entropy alloy comprises the following steps:
[0044] (1) Preparation of Ti / Zr intermediate alloy ingot: weigh according to the preset component ratio, respectively take industrial-grade Ti: 15.1 g, Zr: 28.9 g, and Nb: 29.4 g, wherein all raw materials are industrial-grade; place 15.1 g of titanium and 28.9 g of zirconium in a crucible, and use electric arc smelting, first, pre-extract the vacuum chamber to 10 -3 Pa, then fill high-purity argon gas (volume purity 99.999%) until the vacuum gauge shows 4×10 4 Pa. The alloy smelting current is 300 A, each smelting for 2 minutes, and after each smelting, the alloy is turned over for re-smelting, and the process is repeated at least 3 times to obtain a Ti / Zr intermediate alloy ingot;
[0045] (2) Preparation of Nb / Mo / W intermediate alloy ingot: respectively take industrial-grade Mo: 9.1 g, and W: 17.5 g, wherein all raw materials are industrial-grade; place 9.1 g of molybdenum and 17.5 g of tungsten in a crucible, and use electric arc smelting, first, pre-extract the vacuum chamber to 10 -4 Pa, then fill high-purity argon gas (volume purity 99.999%) until the vacuum gauge shows 8×10 4 Pa. The alloy smelting current is 600 A, each smelting for 2 minutes, and after each smelting, the alloy is turned over for re-smelting, and the process is repeated at least 5 times until the alloy composition is uniform to obtain a Nb / Mo / W intermediate alloy ingot;
[0046] (3) Preparation of master alloy ingot: mix the Ti / Zr intermediate alloy ingot and the Nb / Mo / W intermediate alloy ingot into the same crucible, and use electric arc smelting, first, pre-extract the vacuum chamber to 10 -4 Pa, then fill high-purity argon gas (volume purity 99.999%) until the vacuum gauge shows 8×10 4 Pa. Then, electric arc smelting is performed, the alloy smelting current is 500 A, each smelting for 2 minutes, and after each smelting, the alloy is turned over for re-smelting, and the process is repeated until the composition is uniform to obtain a TiZrNbMo 0.3 W 0.3 master alloy ingot.
[0047] As Figure 1 shown, the as-cast TiZrNbMo 0.3 W 0.3The refractory high-entropy alloy has a dual body-centered cubic structure, and the two phases have a small lattice constant difference co-grain interface. The lattice constant of the matrix is 0.3369 nm, and the lattice constant of the precipitated phase is 0.3279 nm. As shown in Figure 2 , micron-sized white precipitated phases are dispersedly distributed in the alloy matrix, the precipitated phase is rich in W element, and presents irregular shape. The results show that the ideal endogenous co-grain micron-sized dispersed precipitated strengthening structure can be obtained by simple arc melting method.
[0048] The wire cutting method is used to cut the cylindrical alloy with a diameter of 3 mm and a height of 3 mm from the as-cast sample as the dynamic compression sample. The dynamic compression experiment is carried out on the Hopkinson pressure bar, and the strain rate is 2825s -1 , 3137s -1 , 3349s -1 , 3735s -1 , and the dynamic compression true stress-strain curve of the alloy is shown in Figure 3 . When the strain rate increases from 2825s -1 to 3735s -1 , the alloy shows obvious strain rate hardening effect. TiZrNbMo 0.3 W 0.3 The dynamic ultimate strength of the refractory high-entropy alloy increases from about 2.10 GPa to as high as about 2.36 GPa, and the uniform elongation increases from about 20% to about 30%. The ultimate strength of the alloy is much higher than that of traditional steel, titanium alloy and high-entropy alloy, and the ultimate strength of the traditional steel, titanium alloy and high-entropy alloy is mostly lower than 2 GPa. In particular, the dynamic ultimate strength of the TiZrNbMo 0.3 W 0.3 refractory high-entropy alloy is at the same level as that of the BMCGs (1.7-2.8 GPa) and WHAs (2.0-2.6 GPa). In addition, the TiZrNbMo 0.3 W 0.3 refractory high-entropy alloy also has excellent dynamic work hardening capacity, and the ductility can reach about 30%. Generally, the ductility of the BMCGs and WHAs is less than about 5% and about 15%, respectively. In comparison, the TiZrNbMo 0.3 W 0.3 refractory high-entropy alloy has the best comprehensive dynamic mechanical properties.
[0049] As shown in Figure 4 , the TiZrNbMo 0.3 W 0.3The excellent dynamic mechanical properties of the refractory high-entropy alloy are attributed to the dispersed distribution of W-rich precipitates. The dispersed distribution of W-rich precipitates has two important influences on the strength and plasticity of the alloy: first, the dispersed distribution of W-rich precipitates can inhibit the formation of long-range ASBs, and the high-frequency interaction between the W-rich precipitates and ABSs prevents the long-range extension of ABSs, as shown in Figure 4 The adiabatic shear band is deflected by the W-rich precipitates, and the W-rich precipitates also cause the microcracks to be deflected at a high frequency, as shown in Figure 4 The deflection of the microcracks is marked, and the high-frequency deflection of the microcracks promotes the dissipation of plastic work during dynamic deformation. Second, the microcracks can be pinned inside the W-rich precipitates, inducing an interface bridging effect, which improves the TiZrNbMo 0.3 W 0.3 The toughness of the refractory high-entropy alloy. In addition to the microcrack deflection effect of the W-rich precipitates, the microcracks also propagate into the W-rich precipitates and are then pinned, as shown in Figure 4 The crack bridging phenomenon causes the local planar segmentation or arcuation of the microcracks between the dispersed distribution of W-rich precipitates, which is similar to the dislocation pinning effect in the precipitation hardening theory. In contrast, the microcracks that pass through the coherent interface and are pinned inside the W-rich precipitates, i.e., the interface bridging effect, have a greater toughening effect than the microcrack deflection effect of the W-rich precipitates. Therefore, the excellent dynamic mechanical properties of the TiZrNbMoW refractory high-entropy alloy with a double body-centered cubic structure are mainly attributed to the hindering effect of the endogenous coherent dispersed distribution of hard W-rich precipitates on ASBs and microcracks.
[0050] The results of the examples show that the double body-centered cubic structure TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties is a dynamic high-strength, high-plasticity and high-toughness metal functional material that is urgently needed in certain extreme service environment fields. The refractory high-entropy alloy has a simple preparation process, low preparation cost, and wide application potential and economic value in extreme service environments such as national defense and security and industrial fields.
[0051] The above description is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application still belongs to the scope of the technical solution of the present application.
Claims
1. A refractory high-entropy alloy with a double-body-centered cubic structure, characterized in that, On an atomic percentage basis, Ti has an atomic percentage of 25-40%, Zr has an atomic percentage of 25-40%, Nb has an atomic percentage of 15-30%, and the sum of the atomic percentages of Mo and W is 15-30%; its microstructure characteristics are as follows: (1) The microstructure is an endogenous, coherent body-centered cubic structure with micron-sized W-rich phases dispersed in the body-centered cubic refractory high-entropy alloy matrix; (2) The W-rich phase is a stable body-centered cubic structure that precipitates in situ in the matrix due to the supersaturated solid solution characteristics of high-entropy alloys. The volume fraction of the W-rich phase is in the range of 30% to 80%. In 1000 s -1 ~6000 s -1 Within the dynamic loading speed range, the room temperature yield strength is 1400~1600MPa, the ultimate strength is 2100~2600MPa, and the uniform elongation is 20~40%.
2. The double-body-centered cubic TiZrNbMoW refractory high-entropy alloy with excellent dynamic mechanical properties according to claim 1, characterized in that, The preparation method for this type of refractory high-entropy alloy is as follows: arc melting of the master alloy ingot, followed by rapid solidification of the ingot using a water-cooled copper crucible.