Novel light high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy and preparation method thereof

Abstract

The invention relates to the technical field of eutectic high-entropy alloys, in particular to a novel light high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy and a preparation method thereof. When the tensile strength of a conventional Al-Cr-Fe-Ni eutectic high-entropy alloy reaches about 1000 MPa, the elongation of the Al-Cr-Fe-Ni eutectic high-entropy alloy is difficult to reach 15%. In order to solve the technical problems, the invention provides the novel light high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy, the chemical components of the Al-Cr-Fe-Ni eutectic high-entropy alloy are designed as AlaCrbFecNid according to the atomic ratio, a is equal to 18, b is equal to 6.85, c is equal to 28, and d is equal to 47.15. The eutectic high-entropy alloy has excellent mechanical properties, the density is only 6.9 g / cm < 3 >, the microstructure is composed of an FCC phase and a BCC phase, the eutectic high-entropy alloy contains an FCC / BCC eutectic structure, and better balance between the strength and plasticity of the alloy is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of eutectic high entropy alloys, and in particular to a novel lightweight and high-strength Al-Cr-Fe-Ni eutectic high entropy alloy and a preparation method thereof. Background Art

[0002] High-entropy alloys (HEAs), a new type of metal material, have broken through the design concepts of traditional alloys. High-entropy alloys (HEAs), also known as multi-principal element alloys, are composed of five or more metals in equal or similar atomic ratios. Due to their high entropy effect, delayed diffusion effect, lattice distortion effect, and cocktail effect, HEAs exhibit high strength, high toughness, low-temperature fracture toughness, and excellent corrosion resistance, demonstrating broad development prospects in industrial manufacturing.

[0003] Eutectic high entropy alloy (EHEA) combines the characteristics of eutectic alloy and high entropy alloy, with excellent properties such as good fluidity, relatively uniform solidification structure composition, controllable structure and small casting defects, and has attracted widespread attention. Today, the eutectic high entropy alloy system is in a stage of continuous development. However, there are few eutectic high entropy alloy systems with good strength and plasticity balance in existing research, and these alloys often require post-processing to improve their performance. Traditional methods of improving the mechanical properties of alloys are mostly to achieve alloy strength improvement by sacrificing plasticity. The common Al-Cr-Fe-Ni eutectic high entropy alloys on the market are Al 0.8 CrFeNi 2.2 High entropy alloys are designed with Al 16 Cr 20 Fe 20 Ni 44 , its tensile strength is around 1000MPa and its elongation is unlikely to exceed 15%. Summary of the Invention

[0004] The problem in the prior art is that when the tensile strength of conventional Al-Cr-Fe-Ni eutectic high entropy alloy reaches about 1000 MPa, its elongation is difficult to reach 15%. In order to solve the above technical problems, the present invention provides a novel lightweight and high-strength Al-Cr-Fe-Ni eutectic high entropy alloy. The chemical composition of the Al-Cr-Fe-Ni eutectic high entropy alloy is designed to be Al a Cr b Fe c Ni d , where 17≤a≤19, b=6.85, c=28, 46.15≤d≤48.15, and a+b+c+d=100.

[0005] Preferably, the Al a Cr b Fec Ni d Among them, a=17, b=6.85, c=28, and d=48.15.

[0006] Preferably, the Al a Cr b Fe c Ni d Among them, a=18, b=6.85, c=28, and d=47.15.

[0007] Preferably, the Al a Cr b Fe c Ni d Among them, a=19, b=6.85, c=28, and d=46.15.

[0008] Preferably, the preparation method of the novel lightweight and high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy comprises the following steps:

[0009] (1) Al, Cr, Fe, and Ni metal elements with a purity of not less than 99.9 wt% are cleaned by ultrasonic oscillation with anhydrous ethanol, acetone, and anhydrous ethanol in sequence to remove impurities such as oil and dirt attached to the surface of the metal elements, and then dried for later use;

[0010] (2) The metal element raw materials treated in step (1) are weighed and proportioned, and are bagged separately for smelting;

[0011] (3) Place the prepared metal raw materials in a crucible of the smelting furnace in the order of the melting point of the metal raw materials from low to high, place the Ti block in another crucible in the same smelting furnace, and draw the vacuum degree in the smelting furnace to no less than 5×10 3 Pa, then fill the smelting furnace with protective gas, and repeat the above vacuuming and filling steps at least twice;

[0012] (4) During vacuum melting, the Ti block in the crucible in the melting furnace is melted first, and then the mixed metal element raw materials in another crucible are vacuum melted. The vacuum melting is carried out under electromagnetic stirring. The melting current is adjusted to completely melt the alloy raw materials to form an alloy. After the vacuum melting is completed, the alloy liquid is cast into a water-cooled copper crucible to obtain a high-entropy alloy plate of the required size.

[0013] Preferably, the ultrasonic oscillation cleaning time is not less than 3 minutes.

[0014] Preferably, in step (3), before placing the metal element raw material into the crucible, the inside and edge of the crucible are first polished smooth with sandpaper until a brass-colored luster is exposed, and then the crucible is wiped clean with absorbent cotton dipped in anhydrous ethanol to prevent the introduction of inclusions.

[0015] Preferably, after the mixed metal element raw materials are melted and stabilized at a melting current of 200A, the melting current is adjusted in increments of 50A. The current does not exceed 400A during the entire melting process. After the alloy plate cools, the plate is turned over and repeatedly melted at least 4 times to ensure uniform alloy composition.

[0016] The present invention has the following beneficial effects:

[0017] (1) The present invention provides a eutectic high entropy alloy Al 18 Cr 6.85 Fe 28 Ni 47.15 , the eutectic high entropy alloy has excellent mechanical properties, and its strength and plasticity are well matched;

[0018] (2) Eutectic high entropy alloy Al obtained by the present invention 18 Cr 6.85 Fe 28 Ni 47.15 The density is only 6.9g / cm 3 , which is higher than the density of other eutectic high entropy alloys (generally 7.2-7.5 g / cm 3 ) is much smaller, showing a significant lightweight advantage;

[0019] (3) Eutectic high entropy alloy Al obtained by the present invention 18 Cr 6.85 Fe 28 Ni 47.15 The microstructure is composed of FCC phase and BCC phase, and contains FCC / BCC eutectic structure, which achieves a good balance between alloy strength and plasticity;

[0020] (4) The present invention adopts arc melting process to prepare eutectic high entropy alloy, which is simple, safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 CrFeNi obtained in Comparative Example 1 2.2 Al 0.8 Microstructure image of a high-entropy alloy.

[0022] Figure 2 CrFeNi obtained in Comparative Example 1 2.2 Al 0.8 Room temperature tensile stress-strain curves of high entropy alloys.

[0023] Figure 3 Al obtained in Example 1 of the present invention 17 Cr 6.85 Fe 28 Ni 48.15 Microstructure image of a high-entropy alloy.

[0024] Figure 4 Al obtained in Example 2 of the present invention 18 Cr 6.85 Fe 28 Ni 47.15 Microstructure image of a high-entropy alloy.

[0025] Figure 5 Al obtained in Example 3 of the present invention 19 Cr 6.85 Fe 28 Ni 46.15 Microstructure image of a high-entropy alloy.

[0026] Figure 6 These are the XRD patterns of the Al-Cr-Fe-Ni high entropy alloy systems obtained in Examples 1-3 of the present invention.

[0027] Figure 7 Room temperature tensile stress-strain curves of the Al-Cr-Fe-Ni high entropy alloy system obtained in Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below with reference to the following examples. However, it should be understood that the following examples are merely illustrative of the embodiments of the present invention and are not intended to limit the scope of the present invention.

[0029] Example 1

[0030] A new type of lightweight and high-strength Al-Cr-Fe-Ni eutectic high entropy alloy, the chemical composition is designed according to the atomic ratio: Al a Cr b Fe c Ni d ; Among them, a = 17, b = 6.85, c = 28, d = 48.15, that is, the high entropy alloy system is represented by Al 17 Cr 6.85 Fe 28 Ni 48.15 , abbreviated as Al17.

[0031] The preparation method of the Al-Cr-Fe-Ni eutectic high entropy alloy comprises the following steps:

[0032] (1) Al, Cr, Fe, and Ni metal elements with a purity of not less than 99.9 wt% were cleaned with anhydrous ethanol, acetone, and anhydrous ethanol in sequence by ultrasonic oscillation for 3 minutes, and then dried for later use;

[0033] (2) The metal element raw material treated in step (1) is 17 Cr 6.85 Fe28 Ni 48.15 Convert the materials into mass ratio and weigh them, then bag them separately for smelting;

[0034] (3) Before placing the metal raw materials into the crucible, first use 800# SiC sandpaper to polish the inside and edge of the crucible until the brass luster is exposed. Then wipe the crucible clean with absorbent cotton dipped in anhydrous ethanol to prevent the entry of inclusions. Place the prepared metal raw materials in a crucible of the smelting furnace in the order of the melting point of the metal raw materials from low to high. Place the Ti block in another crucible in the same smelting furnace. Pump the vacuum degree in the smelting furnace to 5×10 3 Pa, then fill the melting furnace with high-purity argon gas, and repeat the above vacuuming and filling steps twice;

[0035] (4) First use a current of 70 to 80A to strike the arc, and then increase the current after the arc is successfully struck. During vacuum melting, first melt the Ti block in the crucible in the melting furnace, and then start vacuum melting the mixed metal element raw material in another crucible. The vacuum melting process is carried out under electromagnetic stirring. After the mixed metal element raw material is melted and stabilized at a melting current of 200A, the melting current is adjusted in increments of 50A. The current does not exceed 400A during the entire melting process, and the melting time is 15 minutes. After the alloy plate is cooled, turn the plate over and repeat the melting 4 times to ensure uniform alloy composition. After the vacuum melting is completed, the alloy liquid is cast into a water-cooled copper crucible to obtain a size of 10×10×70mm. 3 high entropy alloy plates.

[0036] The high entropy alloy plate obtained in Example 1 was subjected to quasi-static tensile mechanical property test at a strain rate of 2×10 - 4 s -1 The room temperature tensile stress-strain curve is shown in the attached figure. Figure 7 As shown. 17 Cr 6.85 Fe 28 Ni 48.15 The high-entropy alloy has a tensile strength of 1007.34 MPa, an elongation of 19.16%, and a yield strength of 548.04 MPa.

[0037] Example 2

[0038] A new type of lightweight and high-strength Al-Cr-Fe-Ni eutectic high entropy alloy, the chemical composition is designed according to the atomic ratio: Al a Cr b Fe c Ni d ; Wherein, a=18, b=6.85, c=28, d=47.15, that is, the high entropy alloy system is represented by Al18 Cr 6.85 Fe 28 Ni 47.15 , abbreviated as Al18.

[0039] The preparation method of the Al-Cr-Fe-Ni eutectic high entropy alloy comprises the following steps:

[0040] (1) Al, Cr, Fe, and Ni metal elements with a purity of not less than 99.9 wt% were cleaned with anhydrous ethanol, acetone, and anhydrous ethanol in sequence by ultrasonic oscillation for 3 minutes, and then dried for later use;

[0041] (2) The metal element raw material treated in step (1) is 18 Cr 6.85 Fe 28 Ni 47.15 Convert the materials into mass ratio and weigh them, then bag them separately for smelting;

[0042] (3) Before placing the metal raw materials into the crucible, first use 800# SiC sandpaper to polish the inside and edge of the crucible until the brass luster is exposed. Then wipe the crucible clean with absorbent cotton dipped in anhydrous ethanol to prevent the entry of inclusions. Place the prepared metal raw materials in a crucible of the smelting furnace in the order of the melting point of the metal raw materials from low to high. Place the Ti block in another crucible in the same smelting furnace. Pump the vacuum degree in the smelting furnace to 5×10 3 Pa, then fill the melting furnace with high-purity argon gas, and repeat the above vacuuming and filling steps twice;

[0043] (4) First use a current of 70 to 80A to strike the arc. After the arc is struck successfully, increase the current. During vacuum melting, first melt the Ti block in the crucible in the melting furnace, and then start vacuum melting the mixed metal element raw material in another crucible. The vacuum melting process is carried out under electromagnetic stirring. After the mixed metal element raw material is melted and stabilized at a melting current of 200A, the melting current is adjusted in increments of 50A. The current does not exceed 400A during the entire melting process, and the melting time is 15 minutes. After the alloy plate cools, turn the plate over and repeatedly melt it 4 times to ensure that the alloy composition is uniform. After the vacuum melting is completed, the alloy liquid is cast into a water-cooled copper crucible to obtain a size of 10×10×70mm. 3 high entropy alloy plates.

[0044] The high entropy alloy plate obtained in Example 2 was subjected to quasi-static tensile mechanical property test at a strain rate of 2×10 - 4 s -1 The room temperature tensile stress-strain curve is shown in the attached manual. Figure 7 As shown. 18Cr 6.85 Fe 28 Ni 47.15 The tensile strength of the high-entropy alloy is 1049.24 MPa, the elongation is 17.37%, and the yield strength is 675.87 MPa, with a good match between strength and plasticity.

[0045] Example 3

[0046] A new type of lightweight and high-strength Al-Cr-Fe-Ni eutectic high entropy alloy, the chemical composition is designed according to the atomic ratio: Al a Cr b Fe c Ni d ; Wherein, a=19, b=6.85, c=28, d=46.15, that is, the eutectic high entropy alloy system is represented by Al 19 Cr 6.85 Fe 28 Ni 46.15 , abbreviated as Al19.

[0047] The preparation method of the Al-Cr-Fe-Ni eutectic high entropy alloy comprises the following steps:

[0048] (1) Al, Cr, Fe, and Ni metal elements with a purity of not less than 99.9 wt% were cleaned with anhydrous ethanol, acetone, and anhydrous ethanol in sequence by ultrasonic oscillation for 3 minutes, and then dried for later use;

[0049] (2) The metal element raw material treated in step (1) is 19 Cr 6.85 Fe 28 Ni 46.15 Convert the materials into mass ratio and weigh them, then bag them separately for smelting;

[0050] (3) Before placing the metal raw materials into the crucible, first use 800# SiC sandpaper to polish the inside and edge of the crucible until the brass luster is exposed. Then wipe the crucible clean with absorbent cotton dipped in anhydrous ethanol to prevent the entry of inclusions. Place the prepared metal raw materials in a crucible of the smelting furnace in the order of the melting point of the metal raw materials from low to high. Place the Ti block in another crucible in the same smelting furnace. Pump the vacuum degree in the smelting furnace to 5×10 3 Pa, then fill the melting furnace with high-purity argon gas, and repeat the above vacuuming and filling steps twice;

[0051] (4) First use a current of 70 to 80A to strike the arc. After the arc is struck successfully, increase the current. During vacuum melting, first melt the Ti block in the crucible in the melting furnace, and then start vacuum melting the mixed metal element raw material in another crucible. The vacuum melting process is carried out under electromagnetic stirring. After the mixed metal element raw material is melted and stabilized at a melting current of 200A, the melting current is adjusted in increments of 50A. The current does not exceed 400A during the entire melting process, and the melting time is 15 minutes. After the alloy plate cools, turn the plate over and repeatedly melt it 4 times to ensure that the alloy composition is uniform. After the vacuum melting is completed, the alloy liquid is cast into a water-cooled copper crucible to obtain a size of 10×10×70mm. 3 high entropy alloy plates.

[0052] The quasi-static tensile mechanical properties test of the eutectic high entropy alloy plate obtained in Example 3 was carried out at a strain rate of 2×10 -4 s -1 The room temperature tensile stress-strain curve is shown in the attached manual. Figure 7 As shown. 19 Cr 6.85 Fe 28 Ni 46.15 The high-entropy alloy has a tensile strength of 1190.52 MPa, an elongation of 14.71%, and a yield strength of 600.35 MPa.

[0053] Comparative Example 1

[0054] Literature Xi Jin, Juan Bi, Lu Zhang, Yang Zhou, Xingyu Du, Yuxin Liang, Bangsheng Li, A new CrFeNi2Al eutectic high entropy alloy system with excellent mechanical properties, Journal of Alloys and Compounds, Volume 770 (2019) 655-661. reported an Al-Cr-Fe-Ni eutectic high entropy alloy, the chemical composition expression of the high entropy alloy is CrFeNi 2.2 Al 0.8 .

[0055] The present invention is based on the CrFeNi reported in the literature 2.2 Al 0.8 The atomic ratio of is prepared as follows:

[0056] (1) Al, Cr, Fe, and Ni metal elements with a purity of not less than 99.9 wt% were cleaned with anhydrous ethanol, acetone, and anhydrous ethanol in sequence by ultrasonic oscillation for 3 minutes, and then dried for later use;

[0057] (2) The metal element raw material treated in step (1) is CrFeNi 2.2 Al 0.8 Convert the materials into mass ratio and weigh them, then bag them separately for smelting;

[0058] (3) Before placing the metal raw materials into the crucible, first use 800# SiC sandpaper to polish the inside and edge of the crucible until the brass luster is exposed. Then wipe the crucible clean with absorbent cotton dipped in anhydrous ethanol to prevent the entry of inclusions. Place the prepared metal raw materials in a crucible of the smelting furnace in the order of the melting point of the metal raw materials from low to high. Place the Ti block in another crucible in the same smelting furnace. Pump the vacuum degree in the smelting furnace to 5×10 3 Pa, then fill the melting furnace with high-purity argon gas, and repeat the above vacuuming and filling steps twice;

[0059] (4) First use a current of 70 to 80A to strike the arc. After the arc is struck successfully, increase the current. During vacuum melting, first melt the Ti block in the crucible in the melting furnace, and then start vacuum melting the mixed metal element raw material in another crucible. The vacuum melting process is carried out under electromagnetic stirring. After the mixed metal element raw material is melted and stabilized at a melting current of 200A, the melting current is adjusted in increments of 50A. The current does not exceed 400A during the entire melting process, and the melting time is 15 minutes. After the alloy plate cools, turn the plate over and repeatedly melt it 4 times to ensure that the alloy composition is uniform. After the vacuum melting is completed, the alloy liquid is cast into a water-cooled copper crucible to obtain a size of 10×10×70mm. 3 high entropy alloy plates.

[0060] The high entropy alloy ingot obtained in Comparative Example 1 was subjected to quasi-static tensile mechanical property test at a strain rate of 2×10 - 3 s -1 The room temperature tensile stress-strain curve is shown in the attached manual. Figure 2 As shown. CrFeNi 2.2 Al 0.8 The high-entropy alloy has a tensile strength of approximately 956 MPa, an elongation of approximately 12%, and a yield strength of 479 MPa.

[0061] Density tests were performed on the eutectic high entropy alloys obtained in Examples 1-3 of the present invention and Comparative Example 1, and the specific test results are shown in Table 1.

[0062] Table 1

[0063] Test items <![CDATA[Density g / cm 3 > Example 1 7.0 Example 2 6.9 Example 3 6.9 Comparative Example 1 7.0

[0064] Microstructure analysis

[0065] Phase analysis of the eutectic high entropy alloy plates obtained in Examples 1-3 was performed, and their XRD patterns are shown in the attached specification. Figure 6 As shown in Figure 2, XRD results show that the three alloys are composed of FCC phase and BCC phase.

[0066] The microstructure of the CrFeNi2.2Al0.8 eutectic high entropy alloy ingot obtained in Comparative Example 1 was analyzed, and its microstructure image is shown in the attached specification. Figure 1 As shown in Figure 2, the microstructure of CrFeNi2.2Al0.8 eutectic high entropy alloy is a eutectic structure formed by FCC / BCC.

[0067] The microstructures of the high entropy alloy plates obtained in Examples 1-3 were analyzed, and the microstructure images thereof were as follows: Figure 3-5 The alloy structure of Al17Cr6.85Fe28Ni48.15 is a hypoeutectic structure formed by the FCC primary phase plus the FCC / BCC eutectic, the alloy structure of Al18Cr6.85Fe28Ni47.15 is a eutectic structure formed by the FCC / BCC eutectic, and the alloy structure of Al19Cr6.85Fe28Ni46.15 is a hypereutectic structure formed by the BCC primary phase plus the FCC / BCC eutectic.

[0068] In summary, the Al18Cr6.85Fe28Ni47.15 obtained in the present invention is a eutectic high entropy alloy with a thermal conductivity of 6.9 g / cm 3 The alloy exhibits low density, a tensile strength of 1049.24 MPa, an elongation of 17.37%, and a yield strength of 675.87 MPa. This alloy exhibits excellent mechanical properties and a good balance between strength and plasticity, resolving the problem of poor strength-plasticity matching in existing eutectic high-entropy alloys. Furthermore, the preparation method of the present invention is simple, non-toxic, safe, and readily available, with high economic value and market prospects.

[0069] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A novel lightweight, high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy, characterized in that: The chemical composition of the Al-Cr-Fe-Ni eutectic high entropy alloy is designed to be Al a Cr b Fe c Ni d , where 17≤a≤19, b=6.85, c=28, 46.15≤d≤48.15, and a+b+c+d=100.

2. A novel lightweight, high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy according to claim 1, characterized in that: The Al a Cr b Fe c Ni d Among them, a=17, b=6.85, c=28, and d=48.

15.

3. A novel lightweight, high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy according to claim 1, characterized in that: The Al a Cr b Fe c Ni d Among them, a=18, b=6.85, c=28, and d=47.

15.

4. A novel lightweight, high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy according to claim 1, characterized in that: The Al a Cr b Fe c Ni d Among them, a=19, b=6.85, c=28, and d=46.

15.

5. A novel lightweight, high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) Al, Cr, Fe and Ni metal elements with a purity of not less than 99.9 wt% are cleaned by ultrasonic oscillation with anhydrous ethanol, acetone and anhydrous ethanol in sequence, and then dried for later use; (2) The metal element raw materials treated in step (1) are weighed and proportioned, and are bagged separately for smelting; (3) Place the prepared metal raw materials in a crucible of the smelting furnace in the order of the melting point of the metal raw materials from low to high, place the Ti block in another crucible in the same smelting furnace, and draw the vacuum degree in the smelting furnace to no less than 5×10 3 Pa, then fill the smelting furnace with protective gas, and repeat the above vacuuming and filling steps at least twice; (4) During vacuum melting, the Ti block in the crucible in the melting furnace is melted first, and then the mixed metal element raw materials in another crucible are vacuum melted. The vacuum melting is carried out under electromagnetic stirring. The melting current is adjusted to completely melt the alloy raw materials to form an alloy. After the vacuum melting is completed, the alloy liquid is cast into a water-cooled copper crucible to obtain a high-entropy alloy plate of the required size.

6. A novel lightweight, high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy according to claim 5, characterized in that: The ultrasonic oscillation cleaning time shall not be less than 3 minutes.

7. The novel lightweight, high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy according to claim 5, characterized in that: In step (3), before placing the metal element raw material into the crucible, first use sandpaper to polish the inside and edges of the crucible until a brass-colored luster is exposed, and then wipe the crucible clean with absorbent cotton dipped in anhydrous ethanol to prevent the introduction of inclusions.

8. The novel lightweight, high-strength Al-Cr-Fe-Ni eutectic high-entropy alloy according to claim 5, characterized in that: After the mixed metal element raw materials are melted and stabilized at a melting current of 200A, the melting current is adjusted in increments of 50A. The current does not exceed 400A during the entire melting process. After the alloy plate cools down, turn the plate over and repeatedly melt it for at least 4 times to ensure uniform alloy composition.

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