Refractory high-entropy alloy and preparation method thereof
By preparing refractory high-entropy alloys with BCC and Laves dual-phase structures, the problem of insufficient strengthening capacity of existing alloys is solved by using vacuum arc smelting technology, and the improvement of high hardness and high yield strength is achieved, which is suitable for high-temperature structural materials.
Patent Information
- Application Number
- CN202411233324.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-04
- Publication Date
- 2024-12-06
AI Technical Summary
The single BCC solid solution phase of existing refractory multi-main alloys results in limited strengthening capacity and cannot meet the comprehensive performance requirements of high-temperature structural materials.
By preparing a refractory high-entropy alloy with a BCC and Laves dual-phase structure, the molar ratio and current gradient of Al, Cr, Ta, Ti and form an alloy with high hardness and high yield strength by using a vacuum arc smelting method.
The high-temperature mechanical properties of the alloy are improved, with a maximum hardness of 760HV, a room temperature compression yield strength of 1714MPa, and a yield strength of 1586MPa at 600℃. By controlling the Al content, the number of Laves phases is expanded, and the scope of application of the alloy is expanded.
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Figure CN119082518A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of high entropy alloys and relates to a refractory high entropy alloy and a preparation method thereof. Background Art
[0002] With the rapid development of aircraft engines and gas turbines, higher requirements are placed on the performance of high-temperature materials. However, the widely used nickel-based high-temperature alloys have an inherent melting point (1300°C) limitation, making it difficult to meet higher usage requirements.
[0003] In recent years, the concept of high entropy alloys has been proposed. High entropy alloys are usually composed of four or more elements in equal or non-equal molar ratios. However, most existing refractory multi-principal alloys (RHEAs, RMEAs) have a single BCC solid solution phase, and the strengthening ability of single-phase materials is limited, which will limit the application of high entropy alloys and fail to meet the comprehensive performance requirements of high-temperature structural materials.
[0004] Therefore, it is necessary to provide a refractory high entropy alloy and a preparation method thereof, so as to improve the strength of the alloy while reducing the amount of plastic sacrifice of the alloy, thereby improving the comprehensive performance of the alloy and enabling the alloy to meet higher usage requirements. Summary of the invention
[0005] In order to overcome the problems in the background technology, the present invention prepares a refractory high entropy alloy strengthened by BCC and Laves dual phases, so as to effectively improve the strength of the alloy on the basis of reducing the plastic sacrifice of the alloy, thereby improving the comprehensive mechanical properties of the alloy.
[0006] In order to achieve the above object, the present invention is implemented by the following technical solutions:
[0007] In one aspect, the present invention provides a method for preparing a refractory high entropy alloy, the method comprising the following steps:
[0008] (1) Pretreatment: Remove the oxide layer on the surface of metal Al, Cr, Ta and Ti, and use anhydrous ethanol to ultrasonically clean the metal. Then, dry the metal, pickle it with acid, and then use clean water to ultrasonically clean the metal. Finally, use anhydrous ethanol to clean it and dry it to obtain clean metal Al, Cr, Ta and Ti.
[0009] (2) Vacuum arc melting: Al, Cr, Ta, and Ti are weighed according to the molar ratio of the refractory high entropy alloy elements, and Al, Cr, Ta, and Ti are placed in a water-cooled copper mold crucible from bottom to top, and vacuum arc melted to obtain an alloy ingot.
[0010] Preferably, in the raw materials, the purity of Al, Cr, Ta and Ti is 99.99%.
[0011] Preferably, in step (1), 400-grit sandpaper is used to remove the surface oxide layer of metals Al, Cr, Ta and Ti.
[0012] Preferably, in step (1), anhydrous ethanol is used for ultrasonic cleaning for 5-10 minutes, and then dried at 80° C. for 1 hour.
[0013] Preferably, in step (1), hydrofluoric acid is used for pickling, and the cleaning time is 5-10 minutes.
[0014] Preferably, in step (1), the metal is ultrasonically cleaned with clean water, the clean water is replaced after every 5-10 minutes of cleaning, and the cleaning is repeated more than 5 times.
[0015] Preferably, in step (1), the product is finally washed with anhydrous ethanol for 5 minutes and then dried at 80° C. for 2 hours.
[0016] As a preferred method, before melting the refractory high entropy alloy, the melting environment is first vacuumed to 5 Pa using a mechanical pump, and then the melting environment is vacuumed to 2×10 -3 Pa, and fill with argon to 0.04-0.05MPa, adjust the arc current to 30-80A.
[0017] Preferably, at the beginning of smelting of the refractory high entropy alloy, the arc striking current is 50-100A. After all Ti is melted, the current is increased to 150-220A, and the alloy ingot is turned over for smelting more than five times. After each turning, the smelting time is not less than 1 minute. When the last turning is performed, the smelting is first maintained at 200A for 5 seconds, and then the current is reduced to 150A and maintained for 5 seconds. Finally, the current is reduced to 50A and maintained for 10 seconds, and then the smelting is terminated. After the alloy ingot has cooled for 10 minutes, the alloy ingot is taken out.
[0018] Another aspect of the present invention provides a refractory high entropy alloy prepared by the above preparation method, wherein the chemical composition of the refractory high entropy alloy is expressed as Al x CrTaTi, the element molar ratio is Al:Cr:Ta:Ti=0.25~1:1:1:1 (i.e. x=0.25~1).
[0019] Beneficial effects of the present invention:
[0020] 1. The present invention prepares a refractory high-entropy alloy with a dual-phase structure of BCC and Laves phase. The Laves phase, as the largest type of intermetallic compound, has a variety of crystal structures, including hexagonal C14, cubic C15 and hexagonal C36, which can improve the high-temperature mechanical properties of the alloy. The alloy is strengthened by the dual-phase structure to improve the comprehensive mechanical properties of the alloy. The maximum hardness of the alloy can reach about 760 HV, the maximum compressive yield strength at room temperature can reach 1714 MPa, and the maximum yield strength can reach 1586 MPa at 600°C.
[0021] 2. The present invention can adjust the amount of Laves phase by adjusting the Al content, and finally achieve control of the ratio between the BCC phase and the Laves phase, thereby obtaining a refractory high-entropy alloy with different mechanical properties, further expanding the application range of the alloy.
[0022] 3. The refractory high entropy alloy of the present invention has fewer constituent elements. A refractory high entropy alloy with good comprehensive mechanical properties can be obtained by using fewer types of elements, which is beneficial to reducing the comprehensive cost of the alloy.
[0023] 4. In the repeated turning over smelting process of the present invention, the last turning over smelting adopts a smelting method of gradient current reduction. The smelting temperature is controlled by gradient current reduction, which can improve the uniformity of alloy ingot composition during ingot cooling and reduce alloy smelting defects. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 The X-ray diffraction (XRD) spectra of Examples 1, 2 and 3 of the present invention are shown.
[0025] Figure 2 This is a scanning electron microscope (SEM) image of the refractory high entropy alloy of Example 1 of the present invention.
[0026] Figure 3 This is a scanning electron microscope (SEM) image of the refractory high entropy alloy of Example 2 of the present invention.
[0027] Figure 4 This is a scanning electron microscope (SEM) image of the refractory high entropy alloy of Example 3 of the present invention.
[0028] Figure 5 It is the Vickers hardness of Examples 1, 2 and 3 of the present invention.
[0029] Figure 6 1 and 2 are room temperature compressive stress-strain curves of Examples 1, 2 and 3 of the present invention.
[0030] Figure 7 This is a physical picture of the alloy ingots of Comparative Example 1 and Example 3 of the present invention. DETAILED DESCRIPTION
[0031] The present invention is further described in detail below in conjunction with specific embodiments.
[0032] All chemical reagents not specifically described in the examples of the present invention were commercially available analytically pure.
[0033] Example 1
[0034] This embodiment prepares a refractory high entropy alloy by the following method:
[0035] (1) Metal blocks of Al, Cr, Ta and Ti with a purity greater than 99.99% are taken, and the four metal blocks are subjected to mechanical rough grinding, anhydrous ethanol ultrasonic cleaning, acid cleaning, clean water ultrasonic cleaning, anhydrous ethanol cleaning and drying in sequence.
[0036] (2) Four metals were taken respectively according to the molar ratio of Al, Cr, Ta and Ti being Al:Cr:Ta:Ti=0.25:1:1:1, and then Al, Cr, Ta and Ti metals were placed in a water-cooled copper mold crucible from bottom to top to reduce the volatilization of the alloy during the smelting process. At the same time, a titanium alloy ingot was placed in the crucible next to it (before starting to melt the refractory high entropy alloy, the titanium alloy ingot was first melted to absorb the remaining oxygen and nitrogen in the furnace chamber), the furnace door was closed, and the power supply, water cooling cycle and vacuum system were turned on; the vacuum degree reached 2×10 -3 After Pa, argon is filled to 0.04MPa, the arc striking current is adjusted to 30A, and the arc striking switch is turned on to start melting; the current is gradually increased to 150A, and after melting for at least 5min, one melting is completed. At this time, the alloy ingot is turned over, and the melting is continued for at least 5min, and then another melting is completed. Similarly, each time a melting is completed, it is turned over, and each alloy ingot is turned over and melted at least five times to ensure the uniformity of the chemical composition; for the last melting, first melt at 200A for 5s, then reduce the current to 150A for 5s, and finally reduce the current to 50A for 10s, then close the melting furnace, end the melting, and after cooling is completed, take out the alloy ingot to obtain a button-shaped ingot of a duplex refractory high entropy alloy.
[0037] The alloy ingot of this embodiment was subjected to X-ray diffraction test, and the results are as follows: Figure 1 As shown, through Figure 1 It can be seen that the alloy ingot contains BCC phase and C14 Laves phase, among which the BCC phase is the matrix phase and the C14 Laves phase is the second phase.
[0038] The microstructure of the alloy ingot of this embodiment was analyzed, and the results are as follows: Figure 2 As shown, through Figure 2It can be seen that the microstructure of the alloy ingot presents an obvious two-phase structure, and the number of BCC phases is significantly greater than that of the second phase. The number of the second phase is counted using software, and the results are shown in Table 1. The number of Laves phases is 33.16%.
[0039] The alloy ingot of this embodiment was subjected to mechanical property analysis, including hardness and compression tests. The results are as follows: Figure 5 , Figure 6 As shown, through Figure 5 It can be seen that the hardness of the alloy ingot in this embodiment is 553.40 HV, the room temperature compressive yield strength is 1449 MPa, and the fracture strain is 13.9%.
[0040] Under the condition of 600° C., the yield strength test of the alloy ingot of this embodiment was carried out, and the yield strength of the alloy ingot of this embodiment was measured to be 1341 MPa.
[0041] Example 2
[0042] This embodiment prepares a refractory high entropy alloy by the following method:
[0043] (1) Metal blocks of Al, Cr, Ta and Ti with a purity greater than 99.99% are taken, and the four metal blocks are subjected to mechanical rough grinding, anhydrous ethanol ultrasonic cleaning, acid cleaning, clean water ultrasonic cleaning, anhydrous ethanol cleaning and drying in sequence.
[0044] (2) Four metals were taken respectively according to the molar ratio of Al, Cr, Ta and Ti being Al:Cr:Ta:Ti=0.50:1:1:1, and then Al, Cr, Ta and Ti metals were placed in a water-cooled copper mold crucible from bottom to top to reduce the volatilization of the alloy during the smelting process. At the same time, a titanium alloy ingot was placed in the crucible next to it (before starting to melt the refractory high entropy alloy, the titanium alloy ingot was first melted to absorb the remaining oxygen and nitrogen in the furnace chamber), the furnace door was closed, and the power supply, water cooling cycle and vacuum system were turned on; the vacuum degree reached 2×10 -3 After Pa, argon is filled to 0.045MPa, the arc striking current is adjusted to 50A, and the arc striking switch is turned on to start melting; the current is gradually increased to 180A, and after melting for at least 5min, one melting is completed. At this time, the alloy ingot is turned over, and the melting is continued for at least 5min, and then another melting is completed. Similarly, each time a melting is completed, it is turned over, and each alloy ingot is turned over and melted at least five times to ensure the uniformity of the chemical composition; for the last melting, first melt at 200A for 5s, then reduce the current to 150A for 5s, and finally reduce the current to 50A for 10s, then close the melting furnace, end the melting, and after cooling is completed, take out the alloy ingot to obtain a button-shaped ingot of a duplex refractory high entropy alloy.
[0045] The alloy ingot of this embodiment was subjected to X-ray diffraction test, and the results are as follows: Figure 1 As shown, through Figure 1 It can be seen that the alloy ingot contains BCC phase and C14 Laves phase, among which the BCC phase is the matrix phase and the C14 Laves phase is the second phase.
[0046] The microstructure of the alloy ingot of this embodiment was analyzed, and the results are as follows: Figure 2 As shown, through Figure 2 It can be seen that the microstructure of the alloy ingot presents an obvious two-phase structure, the number of BCC phases is significantly greater than the number of second phases, and compared with Example 1, the number of second phases in the alloy ingot of this embodiment increases; the number of second phases is counted using software, and the results are shown in Table 1, and the number of Laves phases is 38.75%.
[0047] The alloy ingot of this embodiment was subjected to mechanical property analysis, including hardness and compression tests. The results are as follows: Figure 5 , Figure 6 As shown, through Figure 5 It can be seen that the hardness of the alloy ingot in this embodiment is 635.67 HV, the room temperature compressive yield strength is 1695 MPa, and the fracture strain is 8.5%.
[0048] Under the condition of 600° C., the yield strength test of the alloy ingot of this embodiment was carried out, and the yield strength of the alloy ingot of this embodiment was measured to be 1485 MPa.
[0049] Example 3
[0050] This embodiment prepares a refractory high entropy alloy by the following method:
[0051] (1) Metal blocks of Al, Cr, Ta and Ti with a purity greater than 99.99% are taken, and the four metal blocks are subjected to mechanical rough grinding, anhydrous ethanol ultrasonic cleaning, acid cleaning, clean water ultrasonic cleaning, anhydrous ethanol cleaning and drying in sequence.
[0052] (2) Four metals were taken respectively according to the molar ratio of Al, Cr, Ta and Ti being Al:Cr:Ta:Ti=0.50:1:1:1, and then Al, Cr, Ta and Ti metals were placed in a water-cooled copper mold crucible from bottom to top to reduce the volatilization of the alloy during the smelting process. At the same time, a titanium alloy ingot was placed in the crucible next to it (before starting to melt the refractory high entropy alloy, the titanium alloy ingot was first melted to absorb the remaining oxygen and nitrogen in the furnace chamber), the furnace door was closed, and the power supply, water cooling cycle and vacuum system were turned on; the vacuum degree reached 2×10 -3After Pa, argon is filled to 0.05MPa, the arc striking current is adjusted to 80A, and the arc striking switch is turned on to start melting; the current is gradually increased to 220A, and after melting for at least 5min, one melting is completed. At this time, the alloy ingot is turned over, and the melting is continued for at least 5min, and then another melting is completed. Similarly, each time a melting is completed, it is turned over, and each alloy ingot is turned over and melted at least five times to ensure the uniformity of the chemical composition; for the last melting, first melt at 200A for 5s, then reduce the current to 150A for 5s, and finally reduce the current to 50A for 10s, then close the melting furnace, end the melting, and after cooling is completed, take out the alloy ingot to obtain a button-shaped ingot of a duplex refractory high entropy alloy.
[0053] The alloy ingot of this embodiment was subjected to X-ray diffraction test, and the results are as follows: Figure 1 As shown, through Figure 1 It can be seen that the alloy ingot contains BCC phase and C14 Laves phase, among which the BCC phase is the matrix phase and the C14 Laves phase is the second phase.
[0054] The microstructure of the alloy ingot of this embodiment was analyzed, and the results are as follows: Figure 2 As shown, through Figure 2 It can be seen that the microstructure of the alloy ingot presents an obvious two-phase structure, the amount of BCC phase is significantly greater than the amount of the second phase, and compared with Example 2, the amount of the second phase of the alloy ingot in this embodiment also shows an increasing trend; the amount of the second phase is counted using software, and the results are shown in Table 1, and the amount of Laves phase is 42.19%.
[0055] The alloy ingot of this embodiment was subjected to mechanical property analysis, including hardness and compression tests. The results are as follows: Figure 5 , Figure 6 As shown, through Figure 5 It can be seen that the hardness of the alloy ingot in this embodiment is 759.82 HV, the room temperature compressive yield strength is 1714 MPa, and the fracture strain is 4.4%.
[0056] Under the condition of 600° C., the yield strength test of the alloy ingot of this embodiment was carried out, and the yield strength of the alloy ingot of this embodiment was measured to be 1586 MPa.
[0057] Table 1
[0058]
[0059] Comparative Example 1
[0060] This comparative example adopts the same method as Example 3 to prepare the alloy ingot, except that: in the last smelting of this comparative example, after smelting at a current of 200 A for 15 seconds, the current is not gradually reduced in the middle, but the current is directly reduced to 50 A, and then the smelting furnace is closed to end the smelting. After cooling is completed, the alloy ingot is taken out to obtain a button-shaped ingot of the alloy.
[0061] The alloy ingots obtained by melting the comparative example 1 and the embodiment 3 are as follows Figure 7 As shown, through Figure 7 It can be seen that there are obvious smelting defects on the surface of the alloy ingot of Comparative Example 1, while the smelting method of Example 3 can reduce the smelting defects of the ingot.
[0062] In summary, the refractory high entropy alloy prepared by the preparation method of the present invention can obtain an alloy with good comprehensive mechanical properties with fewer constituent elements, and within the range that meets the composition requirements of the refractory high entropy alloy, increasing the Al content can increase the amount of Laves phase in the alloy, thereby achieving the purpose of regulating the amount of Laves phase by regulating the Al content, and obtaining alloys with different mechanical properties through a simple method to meet the requirements of different application scenarios.
[0063] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.
Claims
1. A method for preparing a refractory high entropy alloy, characterized in that: The preparation method comprises the following steps: (1) Pretreatment: remove the surface oxide layer of metal Al, Cr, Ta and Ti, and use anhydrous ethanol to ultrasonically clean the metal, then dry the metal, pickle it, and then use clean water to ultrasonically clean the metal, and finally use anhydrous ethanol to clean it, and then dry it to obtain clean metal Al, Cr, Ta, and Ti; (2) Vacuum arc melting: Al, Cr, Ta, and Ti are weighed according to the molar ratio of the refractory high entropy alloy elements, and Al, Cr, Ta, and Ti are placed in a water-cooled copper mold crucible from bottom to top, and vacuum arc melted to obtain an alloy ingot.
2. The method for preparing a refractory high entropy alloy according to claim 1, characterized in that: Among the raw materials, the purity of Al, Cr, Ta and Ti is 99.99%.
3. The method for preparing a refractory high entropy alloy according to claim 1, characterized in that: In the step (1), 400-grit sandpaper is used to remove the surface oxide layers of the metals Al, Cr, Ta and Ti.
4. The method for preparing a refractory high entropy alloy according to claim 1, characterized in that: In the step (1), anhydrous ethanol is used for ultrasonic cleaning for 5-10 minutes, and then dried at 80° C. for 1 hour.
5. The method for preparing a refractory high entropy alloy according to claim 1, characterized in that: In the step (1), hydrofluoric acid is used for pickling, and the cleaning time is 5-10 minutes.
6. The method for preparing a refractory high entropy alloy according to claim 1, characterized in that: In the step (1), clean water is used to ultrasonically clean the metal, and the clean water is replaced after each cleaning for 5-10 minutes, and the cleaning is repeated for more than 5 times.
7. The method for preparing a refractory high entropy alloy according to claim 1, characterized in that: In the step (1), the sample is finally washed with anhydrous ethanol for 5 minutes and then dried at 80° C. for 2 hours.
8. The method for preparing a refractory high entropy alloy according to claim 1, characterized in that: Before melting the refractory high entropy alloy, the melting environment was first vacuumed to 5 Pa using a mechanical pump, and then vacuumed to 2×10 -3 Pa, and fill with argon to 0.04-0.05MPa, adjust the arc current to 30-80A.
9. The method for preparing a refractory high entropy alloy according to claim 1, characterized in that: At the beginning of smelting of refractory high entropy alloy, the arc striking current is 50-100A. After all Ti is melted, the current is increased to 150-220A, and the alloy ingot is turned over for melting for more than five times. After each turning, the melting time is not less than 1min. When turning over for the last time, first keep melting at 200A for 5s, then reduce the current to 150A and keep melting for 5s, and finally reduce the current to 50A for 10s to end the melting. After the alloy ingot cools for 10min, take out the alloy ingot.
10. The refractory high entropy alloy prepared by the method for preparing a refractory high entropy alloy according to any one of claims 1 to 9, characterized in that: The chemical composition expression of the refractory high entropy alloy is Al x CrTaTi, element molar ratio is Al:Cr:Ta:Ti=0.25~1:1:1:1.