Lightweight high-strength multi-principal-element alloy with ultrahigh specific strength and preparation method of lightweight high-strength multi-principal-element alloy

Abstract

The invention discloses a lightweight high-strength multi-principal-element alloy with ultrahigh specific strength and a preparation method thereof, and belongs to the technical field of multi-principal-element alloys. The preparation method comprises the following steps: selecting four elements of Ti, V, Zr and Al, weighing according to atomic percent, and obtaining a TiVZrAl alloy ingot by adopting a vacuum arc melting method; the TiVZrAl alloy ingot is subjected to homogenization heat treatment; performing multi-pass cold rolling on the homogenized alloy, and then performing recrystallization annealing; performing multi-pass cold rolling on the annealed alloy; and the cold-rolled alloy is subjected to aging treatment, a nanometer amplitude modulation decomposition structure is introduced, and the nanometer structure heterogeneity and nanometer chemical heterogeneity enhanced light-weight high-strength multi-principal-element alloy is obtained. According to the invention, through reasonable element screening and proportion regulation and control, a nano amplitude-modulated decomposition structure is introduced into the alloy to form the nano-structure heterogeneity and nano-chemical heterogeneity reinforced aging-state alloy, so that the problems of insufficient specific strength and mutual restriction of strength and plasticity of the existing multi-principal-element alloy are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-principal element alloys, and particularly relates to a lightweight high-strength multi-principal element alloy with ultra-high specific strength and a preparation method thereof. Background Art

[0002] Lightweight high-strength structural materials can reduce the weight of load-bearing components and have wide applications in the fields of aerospace and new energy lightweighting. At present, the mainly applied lightweight alloy systems include titanium alloys, aluminum alloys, and magnesium alloys, providing important material support for realizing component weight reduction and improving energy utilization efficiency. However, the traditional alloy design concept limits the space for improving the mechanical properties of structural materials and restricts the further development of lightweight high-strength alloys. As a brand-new alloy design concept, multi-principal element alloys can greatly expand the space for alloy composition design and microstructure control, providing a new direction for the development of advanced lightweight high-strength structural materials.

[0003] To develop a lightweight high-strength multi-principal element alloy with excellent mechanical properties, it is necessary to introduce strengthening mechanisms with significant strengthening effects in the alloy microstructure, such as precipitation strengthening, dislocation strengthening, and nanocrystalline strengthening, etc. However, high-hardness precipitates will cause stress concentration, leading to rapid crack initiation. In addition, due to the lack of deformation mechanisms, nanoscale grains and high-density dislocations will cause necking in the early stage of alloy deformation. Therefore, when the alloy strength is significantly improved through the above traditional strengthening mechanisms, it is often accompanied by a sharp drop in plasticity.

[0004] Therefore, it is necessary to provide a lightweight high-strength multi-principal element alloy with ultra-high specific strength and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide a lightweight high-strength multi-principal element alloy with ultra-high specific strength and a preparation method thereof to solve the problems of insufficient specific strength and the mutual restriction between strength and plasticity of current multi-principal element alloys.

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

[0007] A lightweight high-strength multi-principal element alloy with ultra-high specific strength, in atomic percentage, the alloy contains Ti: 50 - 55%, V: 26 - 30%, Zr: 13 - 15%, Al: 4 - 6%, and the density of the alloy < 5.3 g / cm 3 .

[0008] A method for preparing the lightweight high-strength multi-principal element alloy with ultra-high specific strength as described above, the method includes the following steps:

[0009] S1. Select four elements, Ti, V, Zr, and Al. Weigh them according to atomic percentages and obtain a TiVZrAl alloy ingot by means of vacuum arc melting. After the alloy ingot cools in the electric arc furnace, flip the alloy ingot and remelt it eight times repeatedly;

[0010] S2. Conduct homogenization heat treatment on the TiVZrAl alloy ingot and cool it with water to obtain a homogenized alloy;

[0011] S3. Conduct multi-pass cold rolling on the homogenized alloy. The reduction per pass of cold rolling is < 15%, and the total reduction of cold rolling is 45 - 65%. Subsequently, conduct recrystallization annealing to obtain an annealed alloy;

[0012] S4. Conduct multi-pass cold rolling on the annealed alloy. The reduction per pass of cold rolling is < 15%, and the total reduction of cold rolling is 80 - 85% to obtain a cold-rolled alloy; and

[0013] S5. Conduct aging treatment on the cold-rolled alloy, introduce a nanostructured modulated decomposition structure into the cold-rolled alloy, and cool it with water to obtain a lightweight, high-strength, multi-principal-element alloy enhanced by nanostructural heterogeneity and nanochemical heterogeneity.

[0014] Further, the process of the heat treatment in step S2 is to hold at 1200 °C for 2 hours.

[0015] Further, the process of the recrystallization annealing in step S3 is to hold at 900 - 1200 °C for 5 - 20 min.

[0016] Further, the process of the aging treatment in step S5 is to hold at 350 - 450 °C for 40 - 50 minutes.

[0017] Further, the temperature of the aging treatment in step S5 is within the modulated decomposition phase region of the cold-rolled alloy.

[0018] Further, for the lightweight, high-strength, multi-principal-element alloy enhanced by nanostructural heterogeneity and nanochemical heterogeneity, the yield strength ≥ 1630 MPa, the tensile strength ≥ 1700 MPa, the elongation ≥ 9%, and the specific strength ≥ 331 MPa·cm 3 ·g -1 .

[0019] The present invention has the following beneficial effects:

[0020] Through reasonable element screening and ratio regulation, the present invention designs a TiVZrAl-based lightweight, high-strength, multi-principal-element alloy with the potential of regulating structure and chemical heterogeneity. The TiVZrAl-based lightweight, high-strength, multi-principal-element alloy is prepared by using a conventional arc melting method. After cold deformation and heat treatment, the annealed alloy has a BCC single-phase structure and uniform element distribution. The alloy density is lower than 5.3 g·cm -3Subsequently, a cold-rolled alloy with a large number of nanocrystalline structures was prepared by cold rolling deformation. The difference in grain size can cause the effect of structural heterogeneity strengthening. Finally, the cold-rolled alloy was subjected to aging treatment to introduce nano-scale modulated decomposition structures into the alloy, forming an aged alloy with nano-structural heterogeneity and nano-chemical heterogeneity strengthening. Under the enhancement of the dual strengthening mechanism, the optimal tensile strength of the alloy reached 1742 MPa, the yield strength reached 1684 MPa, the elongation reached 11%, and the specific strength reached 338 MPa·cm 3 ·g -1 , and its mechanical properties are significantly higher than those of other high-entropy alloys, solving the problems of insufficient specific strength and the mutual restriction between strength and plasticity of current high-entropy alloys. The TiVZrAl-based lightweight high-entropy alloy with nano-structural heterogeneity and nano-chemical heterogeneity enhancement in the present invention has ultra-high specific strength and excellent strength-plasticity matching, and will have important applications in the field of lightweight such as aerospace. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the electron backscatter diffraction inverse pole figure (EBSD IPF map) of the annealed Ti 52 V 29 Zr 14 Al 5 alloy in the embodiment of the present invention;

[0022] Figure 2 is the microstructure of the cold-rolled Ti 52 V 29 Zr 14 Al 5 alloy in the embodiment of the present invention. Wherein, Figure a is the EBSD IPF map; Figures b and c are transmission electron microscope pictures (TEM pictures) within the nanocrystalline band;

[0023] (Note: Figure 2 The black banded structure in a is the nanocrystalline band. Since the nanocrystalline size is smaller than the minimum step size of EBSD, it is shown as an unrecognized black stripe)

[0024] Figure 3 is the microstructure of the aged Ti 52 V 29 Zr 14 Al 5 alloy in the embodiment of the present invention. Wherein, Figure a is the high-angle annular dark field scanning transmission electron microscope image (STEM-HADDF image) of the nano-scale modulated decomposition structure; Figure b is the corresponding selected electron diffraction pattern; Figures c-f are the energy dispersive X-ray spectroscopy area scan images (EDS-mapping images) of the nano-scale modulated decomposition structure;

[0025] Figure 4 is Ti in the embodiment of the present invention 52 V 29Zr 14 Al 5 Tensile stress-strain curves of the alloy in annealed, cold rolled and aged states. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0027] The present invention utilizes the flexible design concept of multi-principal alloy to introduce a high-quality strengthening mechanism that takes into account both strength and plasticity in the alloy, and provides a lightweight and high-strength multi-principal alloy with ultra-high specific strength. In terms of atomic percentage, the alloy contains Ti: 50-55%, V: 26-30%, Zr: 13-15%, Al: 4-6%, and the density of the alloy is less than 5.3g / cm 3 .

[0028] The present invention also provides a method for preparing the above-mentioned lightweight and high-strength multi-principal-component alloy with ultra-high specific strength, comprising the following steps:

[0029] S1, select Ti, V, Zr, Al four elements, weigh them according to atomic percentage, and use vacuum arc melting method to obtain TiVZrAl alloy ingot. In order to make the alloy ingot composition uniform, after the alloy ingot is cooled in the arc furnace, turn the alloy ingot over and repeatedly melt it eight times;

[0030] S2, subjecting the TiVZrAl alloy ingot to homogenization heat treatment, wherein the heat treatment process comprises maintaining the temperature at 1200° C. for 2 hours and water cooling to obtain a homogenized alloy;

[0031] S3, performing multiple cold rolling on the homogenized alloy, wherein the cold rolling reduction in each pass is less than 15%, and the total cold rolling reduction is 45-65%, followed by recrystallization annealing, wherein the recrystallization annealing process is 900-1200° C. for 5-20 min, to obtain an annealed alloy;

[0032] S4, performing multiple cold rolling on the annealed alloy, wherein the cold rolling reduction in each pass is less than 15% and the total cold rolling reduction is 80-85%, to obtain a cold rolled alloy; and

[0033] S5, subjecting the cold-rolled alloy to aging treatment, introducing nano-spindle decomposition structure into the cold-rolled alloy, the aging treatment process is 350-450°C for 40-50 minutes, wherein the aging treatment temperature is in the spindle decomposition phase region of the cold-rolled alloy, water cooling, to obtain a lightweight, high-strength, multi-principal alloy with nano-structural heterogeneity and nano-chemical heterogeneity reinforcement.

[0034] The yield strength of the lightweight, high-strength multi-principal alloy reinforced by nanostructure heterogeneity and nanochemical heterogeneity is ≥1630MPa, the tensile strength is ≥1700MPa, the elongation is ≥9%, and the specific strength is ≥331MPa·cm3 ·g -1 。

[0035] Example 1

[0036] Refer to Figures 1-4 , for the lightweight and high-strength multi-principal element alloy of this example, the atomic percentages of its constituent elements are: Ti 52 V 29 Zr 14 Al 5 . Pure metals titanium, vanadium, zirconium and aluminum with a purity exceeding 99.9% are obtained through conventional vacuum arc melting to obtain alloy ingots, and the alloy density is 5.16 g·cm -3 .

[0037] S1. Homogenize the as-cast alloy. The heat treatment temperature is 1200 °C, the holding time is two hours, and water cooling is carried out to obtain the homogenized alloy.

[0038] S2. Cold roll the homogenized alloy. The cold rolling deformation per pass is 10-15%, and the final total cold rolling deformation is controlled to be 60%.

[0039] S3. Recrystallization anneal the cold-rolled alloy with a 60% reduction. The annealing temperature is 1200 °C, and the holding time is 5 minutes. The microstructure of the annealed alloy is as Figure 1 shown.

[0040] S4. Cold roll and deform the annealed alloy. The cold rolling deformation per pass is 10-15%, and the final total cold rolling deformation is controlled to be 80%. The microstructure of the cold-rolled alloy is as Figure 2 shown.

[0041] S5. Age the cold-rolled alloy. The aging temperature is 400 °C, and the holding time is 45 minutes. The microstructure of the aged alloy is as Figure 3 shown, forming a nanocrystalline structure and a spinodal decomposition structure.

[0042] Under room temperature conditions, tensile mechanical property tests are carried out on the aged multi-principal element alloy, and its tensile stress-strain curve is as Figure 4 shown. The tensile strength reaches 1742 MPa, the yield strength reaches 1684 MPa, the elongation reaches 11%, and the specific strength reaches 338 MPa·cm 3 ·g -1 .

[0043] Example 2

[0044] For the lightweight and high-strength multi-principal element alloy of this example, the atomic percentages of its constituent elements are: Ti 52 V 30 Zr 13 Al5 Pure metallic titanium, vanadium, zirconium, and aluminum with a purity exceeding 99.9% are used to obtain alloy ingots through conventional vacuum arc melting. The alloy density is 5.15 g·cm -3 。

[0045] S1. The as-cast alloy is homogenized. The heat treatment temperature is 1200 °C, and the holding time is two hours. Water cooling is carried out to obtain the homogenized alloy.

[0046] S2. The homogenized alloy is cold-rolled. The cold-rolling deformation per pass is 10 - 15%, and the total cold-rolling deformation is finally controlled to be 60%.

[0047] S3. The cold-rolled alloy with a 60% reduction is subjected to recrystallization annealing. The annealing temperature is 1000 °C, and the holding time is 10 minutes.

[0048] S4. The annealed alloy is cold-rolled. The cold-rolling deformation per pass is 10 - 15%, and the total cold-rolling deformation is finally controlled to be 80%.

[0049] S5. The cold-rolled alloy is solution-treated. The solution treatment temperature is 400 °C, and the holding time is 45 minutes.

[0050] At room temperature, the tensile mechanical properties of the solution-treated multi-principal element alloy are tested. The tensile strength reaches 1715 MPa, the yield strength reaches 1651 MPa, the elongation reaches 9%, and the specific strength reaches 333 MPa·cm 3 ·g -1 。

[0051] Example 3

[0052] For the lightweight and high-strength multi-principal element alloy of this example, the atomic percentages of its constituent elements are: Ti 54 V 26 Zr 15 Al 5 Pure metallic titanium, vanadium, zirconium, and aluminum with a purity exceeding 99.9% are used to obtain alloy ingots through conventional vacuum arc melting. The alloy density is 5.15 g·cm -3 。

[0053] S1. The as-cast alloy is homogenized. The heat treatment temperature is 1200 °C, and the holding time is two hours. Water cooling is carried out to obtain the homogenized alloy.

[0054] S2. The homogenized alloy is cold-rolled. The cold-rolling deformation per pass is 10 - 15%, and the total cold-rolling deformation is finally controlled to be 60%.

[0055] S3. The cold-rolled alloy with a 60% reduction is subjected to recrystallization annealing. The annealing temperature is 1200 °C, and the holding time is 5 minutes.

[0056] S4. Cold roll the annealed alloy, with the cold rolling deformation per pass being 10 - 15%, and finally control the total cold rolling deformation to be 80%.

[0057] S5. Perform aging treatment on the cold - rolled alloy, with the aging temperature being 400 °C and the holding time being 45 minutes.

[0058] At room temperature, perform tensile mechanical property tests on the cold - rolled multi - principal - element alloy. Its tensile strength reaches 1704 MPa, the yield strength reaches 1636 MPa, the elongation reaches 10%, and the specific strength reaches 331 MPa·cm 3 ·g -1 .

[0059] Comparative Example 1

[0060] For the lightweight and high - strength multi - principal - element alloy of this example, the alloy composition is the same as that of Example 1. Pure metals titanium, vanadium, zirconium, and aluminum with a purity exceeding 99.9% are used to obtain an alloy ingot through conventional vacuum arc melting. The alloy density is 5.16 g·cm -3 .

[0061] S1. Perform homogenization treatment on the as - cast alloy. The heat treatment temperature is 1200 °C, the holding time is two hours, and water - cooling is used to obtain the homogenized alloy.

[0062] S2. Cold roll the homogenized alloy, with the cold rolling deformation per pass being 10 - 15%, and finally control the total cold rolling deformation to be 60%.

[0063] S3. Perform recrystallization annealing on the cold - rolled alloy with a 60% reduction. The annealing temperature is 1200 °C and the holding time is 5 minutes. The microstructure of the annealed alloy is as Figure 1 shown. The annealed alloy is a single - phase BCC structure, and there are no nanocrystalline structures and spinodal decomposition structures in the alloy microstructure.

[0064] At room temperature, perform tensile mechanical property tests on the annealed multi - principal - element alloy. Its tensile stress - strain curve is as Figure 4 shown. The tensile strength reaches 1012 MPa, the yield strength reaches 1041 MPa, and the elongation reaches 18%.

[0065] Comparative Example 2

[0066] For the lightweight and high - strength multi - principal - element alloy of this example, the alloy composition is the same as that of Example 1. Pure metals titanium, vanadium, zirconium, and aluminum with a purity exceeding 99.9% are used to obtain an alloy ingot through conventional vacuum arc melting. The alloy density is 5.16 g·cm -3 .

[0067] S1. Homogenize the as-cast alloy at a heat treatment temperature of 1200 °C for 2 hours, followed by water cooling to obtain the homogenized alloy.

[0068] S2. Cold roll the homogenized alloy with a cold rolling deformation of 10 - 15% per pass, and finally control the total cold rolling deformation to 60%.

[0069] S3. Recrystallize anneal the cold-rolled alloy with a 60% reduction in thickness at an annealing temperature of 1200 °C for 5 minutes. The microstructure of the annealed alloy is as Figure 1 shown.

[0070] S4. Cold roll the annealed alloy with a cold rolling deformation of 10 - 15% per pass, and finally control the total cold rolling deformation to 80%. The microstructure of the cold-rolled alloy is as Figure 2 shown, and a nanocrystalline structure is formed in the alloy without spinodal decomposition structure.

[0071] Tensile mechanical property tests were carried out on the cold-rolled multi-principal element alloy at room temperature. The tensile stress-strain curve is as Figure 4 shown, with a tensile strength of 1530 MPa, a yield strength of 1485 MPa, and an elongation of 10%.

[0072] In the above Example 1, Comparative Example 1, and Comparative Example 2, age-hardened, annealed, and cold-rolled Ti 52 V 29 Zr 14 Al 5 multi-principal element alloys were obtained respectively. By comparing the mechanical properties of the annealed state (Comparative Example 1) and the cold-rolled alloy (Comparative Example 2), after cold deformation, the strength of the Ti 52 V 29 Zr 14 Al 5 multi-principal element alloy is significantly improved, but the plasticity decreases. The significant strength improvement benefits from the strengthening of the network nanocrystalline bands in the structure, but the remaining dislocations also reduce the plasticity of the alloy. Subsequently, the cold-rolled alloy was age-hardened, and the strength of the alloy continued to increase after aging without losing plasticity, which benefits from the strengthening effect brought by spinodal decomposition. Finally, the lightweight multi-principal element alloy with co-enhanced nano-structural heterogeneity and nano-chemical heterogeneity achieved excellent strength-ductility matching and ultra-high specific strength.

[0073] Through reasonable element screening and ratio regulation, the present invention designs a TiVZrAl-based lightweight high-strength multi-principal element alloy with the potential for regulating structure and chemical heterogeneity. The TiVZrAl-based lightweight high-strength multi-principal element alloy was prepared by a conventional arc melting method. After cold deformation and heat treatment, the annealed alloy has a BCC single-phase structure and uniform element distribution, and the alloy density is lower than 5.3 g·cm -3Subsequently, a cold-rolled alloy with a large number of nanocrystalline structures was prepared by cold rolling deformation. The grain size difference can cause the structural heterogeneity strengthening effect. Finally, the cold-rolled alloy was aged to introduce nano-scale modulated decomposition structures in the alloy, forming an aged alloy with nano-structural heterogeneity and nano-chemical heterogeneity strengthening. Under the enhancement of the dual strengthening mechanism, the optimal tensile strength of the alloy reaches 1742 MPa, the yield strength reaches 1684 MPa, the elongation reaches 11%, and the specific strength reaches 338 MPa·cm 3 ·g -1 , and its mechanical properties are significantly higher than those of other high-entropy alloys, solving the problems of insufficient specific strength and the mutual restriction between strength and plasticity of current high-entropy alloys.

[0074] The TiVZrAl-based lightweight high-entropy alloy with nano-structural heterogeneity and nano-chemical heterogeneity enhancement in the present invention has ultra-high specific strength and excellent strength-plasticity matching, and will have important applications in the field of lightweight such as aerospace.

[0075] The embodiments described above are only used to describe 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 lightweight, high-strength, multi-principal alloy with ultra-high specific strength, characterized in that: In terms of atomic percentage, the alloy comprises Ti: 50-55%, V: 26-30%, Zr: 13-15%, Al: 4-6%, and the density of the alloy is less than 5.3 g / cm 3 .

2. A method for preparing the lightweight, high-strength, multi-principal-component alloy with ultra-high specific strength according to claim 1, characterized in that: The method comprises the following steps: S1, selecting four elements, Ti, V, Zr, and Al, weighing them according to atomic percentage, and obtaining a TiVZrAl alloy ingot by a vacuum arc melting method, and after the alloy ingot is cooled in an arc furnace, turning the alloy ingot over and repeatedly melting it eight times; S2, subjecting the TiVZrAl alloy ingot to homogenization heat treatment and water cooling to obtain a homogenized alloy; S3, performing multiple cold rolling on the homogenized alloy, wherein the cold rolling reduction in each pass is less than 15% and the total cold rolling reduction is 45-65%, and then performing recrystallization annealing to obtain an annealed alloy; S4, performing multiple cold rolling on the annealed alloy, wherein the cold rolling reduction in each pass is less than 15% and the total cold rolling reduction is 80-85%, to obtain a cold rolled alloy; and S5, subjecting the cold-rolled alloy to aging treatment, introducing nano-spindle decomposition structure into the cold-rolled alloy, and water cooling to obtain a lightweight, high-strength, multi-principal-component alloy with nano-structural heterogeneity and nano-chemical heterogeneity reinforcement.

3. The method according to claim 2, characterized in that The heat treatment process in step S2 is to keep the temperature at 1200° C. for 2 hours.

4. The method according to claim 2, characterized in that: The recrystallization annealing process in step S3 is to keep the temperature at 900-1200° C. for 5-20 minutes.

5. The method according to claim 2, characterized in that: The aging treatment process in step S5 is to keep the temperature at 350-450° C. for 40-50 minutes.

6. The method according to claim 2, characterized in that The temperature of the aging treatment in step S5 is located in the spinodal decomposition phase region of the cold-rolled alloy.

7. The method according to claim 2, characterized in that: The yield strength of the lightweight high-strength multi-principal alloy enhanced by nanostructure heterogeneity and nanochemical heterogeneity is ≥1630MPa, the tensile strength is ≥1700MPa, the elongation is ≥9%, and the specific strength is ≥331MPa·cm 3 ·g -1 .

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