High modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin films and their preparation methods

Abstract

A high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film and its preparation method are disclosed, belonging to the field of high-entropy shape memory alloy technology. The specific chemical composition of this high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film is Ti... 16.67 Zr 16.67 Hf 16.67 Co 16.67 Ni 16.67 Cu 16.67 The prepared high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film achieved a hardness of up to 75 GPa and an elastic modulus of up to 935 GPa. The film exhibits high crystallinity, with fine-sized, uniformly distributed equiaxed grains. The preparation method employed was ultra-high vacuum DC magnetron sputtering, a method with broad applicability.

Description

Technical Field

[0001] This invention relates to the field of high-entropy shape memory alloy technology, and particularly to a high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film and its preparation method. The high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film has a chemical composition of Ti. 16.67 Zr 16.67 Hf 16.67 Co 16.67 Ni 16.67 Cu 16.67 High-entropy shape memory alloy thin films. Background Technology

[0002] In recent years, with the rapid development of aerospace, biomedicine, military equipment, and intelligent manufacturing, the requirements for the strength, hardness, modulus, cycle stability, corrosion resistance, and fatigue resistance of shape memory thin film materials in microelectromechanical and microelectronic systems have been increasing. Currently, the improvement of these properties by commonly used binary or ternary thin film materials through methods such as adjusting composition and element doping has reached a bottleneck and is insufficient to meet current demands. Therefore, this paper considers introducing the concept of high-entropy alloys into shape memory thin film materials. The severe lattice distortion effect generated by the "high-entropy effect" can further induce solid solution strengthening, thereby improving the alloy's yield strength and hardness, extending fatigue life, and enhancing corrosion resistance and fatigue resistance.

[0003] Since the discovery of Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory alloys in 2015, which exhibit excellent superelasticity, shape memory effect, and cycle stability, they have attracted widespread attention. Consequently, the idea of ​​incorporating this material system into shape memory films has emerged. However, currently prepared Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory films are all in an amorphous glassy state, with low crystallinity, hardness, and elastic modulus. The hardness of amorphous glassy films is only ~10 GPa, and the elastic modulus is ~130 GPa, making it impossible to generate superelasticity and shape memory effects. Therefore, how to prepare Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory films with high crystallinity, high modulus, and high hardness is an urgent problem to be solved. Summary of the Invention

[0004] To address the problems of the prior art, this invention proposes a high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film and its preparation method. The preparation method of the high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film is a method for preparing high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film using ultra-high vacuum DC magnetron sputtering. The high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film prepared by this invention is a crystalline film with particularly high hardness and elastic modulus. Traditional Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory films are amorphous glassy films with a hardness of only ~10 GPa and an elastic modulus of ~130 GPa. The high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film prepared by this invention has a hardness as high as 75 GPa and an elastic modulus as high as 935 GPa. The high performance is due to the high crystallinity inside the film, with small equiaxed crystals that are evenly distributed.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention discloses a high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film, wherein Ti-Zr-Hf-Co-Ni-Cu is in equiatomic percentage, and the specific chemical composition is Ti 16.67 Zr 16.67 Hf 16.67 Co 16.67 Ni 16.67 Cu 16.67 .

[0007] The high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film has an elastic modulus of 592-935 GPa and a hardness of 43-75 GPa. The film has a single-phase crystalline structure with 200-300 nm nanocrystals in its microstructure. The nanocrystals are B2 ordered phase (BCC structure) with a crystallinity higher than 90%.

[0008] The present invention discloses a method for preparing a high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film, which is prepared by ultra-high vacuum DC magnetron sputtering and the crystallinity, elastic modulus and hardness of the film are adjusted by changing the substrate temperature and sputtering power.

[0009] The substrate temperature is 20–200℃, and the sputtering power is 150W–200W.

[0010] The method for preparing high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin films according to the present invention specifically includes the following steps:

[0011] S1: Select a single crystal silicon wafer as the substrate and perform surface treatment to obtain a single-sided polished single crystal silicon wafer with 140-160μm SiO2 on the surface. Then remove impurities and dry it to obtain the substrate after impurity removal.

[0012] In S1, the size of the single-crystal silicon wafer is 15mm × 15mm.

[0013] In S1, the impurity removal process involves first sonicating with acetone for at least 30 minutes, then sonicating with alcohol for at least 30 minutes, and finally rinsing with deionized water until the surface is clean.

[0014] In S1, the drying process is performed using an argon gas flow.

[0015] S2: Place the cleaned substrate in the mold with the polished surface facing down, insert it horizontally into the ultra-high vacuum magnetron sputtering system, and use a baffle to block the substrate;

[0016] S3: Fix the TiZrHfCoNiCu alloy target material with an equiatomic percentage onto a DC power supply;

[0017] In S3, the TiZrHfCoNiCu alloy target is prepared by powder metallurgy.

[0018] S4: Use mechanical and molecular pumps to evacuate the vacuum to 10. -5 Below Pa, high-purity argon gas is introduced at a flow rate of 20-30 sccm to maintain the gas pressure in the cavity at 0.2-0.5 Pa for glow discharge cleaning for 30-60 minutes.

[0019] S5: Keep argon gas inlet, adjust sputtering power to 150W-200W, pre-sputter for 30-60 minutes, and remove surface impurities on the target.

[0020] S6: After pre-sputtering, maintain the working pressure in the cavity of the ultra-high vacuum magnetron sputtering system at 0.5-0.7 Pa, the argon flow rate at 20-30 sccm, the substrate bias voltage at 0V, and the substrate temperature at 20-200℃. Remove the baffle above the substrate to begin formal sputtering. At the same time, turn on the substrate 360° rotation switch and set the rotation speed to 50-80 sccm to maintain sputtering uniformity. Continue sputtering for 30 min to 2 h, and cool with the furnace to obtain a high modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film.

[0021] In the above preparation method, the high-purity argon gas conforms to the national standard GB / T 10624-1995, with an argon purity >99.999%, nitrogen content <5ppm, oxygen content <2ppm, hydrogen content <1ppm, total carbon content (calculated as methane) <2ppm, and moisture content <4ppm.

[0022] The present invention has the following advantages:

[0023] 1. This method can be used to obtain high-entropy shape memory films of high crystallinity, high modulus and hardness in crystalline Ti-Zr-Hf-Co-Ni-Cu;

[0024] 2. The elastic modulus of the high-modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film prepared by this method can reach 928.9 GPa and the hardness can reach 71.3 GPa.

[0025] 3. Since DC magnetron sputtering is a rapid solidification process, due to the excessively fast solidification rate, amorphous glassy states are easily formed during the preparation of high-entropy alloy thin films with large atomic size differences (exceeding 13%). However, this invention achieves the preparation of high-entropy shape memory thin films with crystalline structures by coordinating and controlling the substrate temperature with sputtering power. This method has universal applicability, so this invention can also be applied to the preparation of other crystalline high-entropy alloy thin films with large atomic size differences. Attached Figure Description

[0026] Figure 1 These are X-ray diffraction (XRD) images of high-modulus and hard crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory films sputtered at 20℃, 100℃, and 200℃.

[0027] Figure 2 These are transmission bright-field images and electron diffraction images of high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory films sputtered at 100℃.

[0028] Figure 3 a is the loading and unloading curve of a high-modulus and hard crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film sputtered at 20℃, 100℃ and 200℃ during nanoindentation testing.

[0029] Figure 3 b is the curve showing the change in elastic modulus and hardness of a high-entropy shape memory thin film of crystalline Ti-Zr-Hf-Co-Ni-Cu with sputtering temperature.

[0030] Figure 4 This is a comparison chart of the elastic modulus and hardness of high-entropy alloy thin films with nanocrystalline structures. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the embodiments.

[0032] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0033] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

[0034] Reference Figure 1 As shown, the high modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory films prepared by the above-mentioned DC magnetron sputtering process are all in a single-phase crystal state with a B2 structure, and no amorphous peaks were found in the XRD images.

[0035] Reference Figure 2 As shown in the transmission bright-field image of a high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film sputtered from a high-temperature substrate, a large number of grains with a size of 200 nm to 300 nm are visible within the microstructure of this film. Analysis of the electron diffraction results in the inset indicates that the grains within the microstructure are of the B2 phase (BCC structure), which is consistent with... Figure 1 The XRD results are consistent.

[0036] Reference Figure 3 As shown in Figure a, the loading-unloading curves of the nanoindentation test of high-modulus and hard crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory films sputtered on substrates with different temperatures show that as the substrate temperature increases, the deformation resistance of the film surface during loading is greater when tested at the same depth, indicating that the elastic modulus and hardness of the film are higher.

[0037] Reference Figure 3 As shown in b, with the increase of substrate temperature, the elastic modulus and hardness of the high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film show an increasing trend. After fitting, it can be determined that the elastic modulus and hardness of the film are linearly related to the substrate temperature. The fitting formulas are: y = 4.39x + 79.58 and z = 0.34x + 5.47, where x represents the sputtering temperature, y represents the elastic modulus, and z represents the hardness.

[0038] Reference Figure 4 As shown, when comparing the high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film sputtered from a high-temperature substrate with other high-entropy alloy films, this film has significant advantages in elastic modulus and hardness.

[0039] Example 1

[0040] High modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin films were prepared by ultra-high vacuum DC magnetron sputtering. TiZrHfCoNiCu high-entropy shape memory alloy targets with equal atomic ratios were placed on a DC power supply for sputtering. The sputtering power was 200W, the sputtering time was 40min, and the substrate temperature was 100℃.

[0041] The XRD characterization results of the obtained high modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin films are as follows: Figure 1 As shown, the results indicate that the film is crystalline, with grain sizes in the microstructure ranging from 200 nm to 300 nm (e.g., ...). Figure 2 As shown), it has a B2 structure, an elastic modulus of 592.6 GPa, and a hardness of 43.6 GPa (as shown). Figure 3 As shown in the figure, it is much higher than other high-entropy alloy films.

[0042] Example 2

[0043] High modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin films were prepared by ultra-high vacuum DC magnetron sputtering. TiZrHfCoNiCu high-entropy shape memory alloy targets with equal atomic ratios were placed on a DC power supply for sputtering. The sputtering power was 170W, the sputtering time was 1h, and the substrate temperature was 150℃.

[0044] The obtained Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film is still crystalline, but the grain size does not show significant changes. The elastic modulus is 700.1 GPa and the hardness is 60.6 GPa.

[0045] Example 3

[0046] High modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin films were prepared by ultra-high vacuum DC magnetron sputtering. The TiZrHfCoNiCu high-entropy shape memory alloy target with equiatomic ratio was placed on a DC power supply for sputtering. The sputtering power was 190W, the sputtering time was 1.5h, and the substrate temperature was 200℃.

[0047] The obtained Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film is still crystalline, but the grain size does not show significant changes. The elastic modulus is 930.2 GPa and the hardness is 70.3 GPa.

[0048] Example 4

[0049] High-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin films were prepared by ultra-high vacuum DC magnetron sputtering. The specific method is as follows:

[0050] 1) Place a single-sided polished monocrystalline silicon wafer with a size of 15mm×15mm and a surface coated with ~150μmSiO2 in acetone and alcohol respectively for 30min, then rinse with deionized water until the surface is clean, and then dry it in an argon flow.

[0051] 2) After cleaning the substrate, place it in the mold and fix it with the polished side facing down. Insert it horizontally into the ultra-high vacuum magnetron sputtering system. At this time, use a baffle to block the substrate.

[0052] 3) Fix the TiZrHfCoNiCu alloy target material with an equal atomic percentage onto a DC power supply;

[0053] 4) Use mechanical pumps and molecular pumps to evacuate the vacuum to 10. -5 After Pa, high-purity argon gas is introduced to maintain the gas pressure in the cavity at 0.2 Pa for glow discharge cleaning for 30 min;

[0054] 5) After confirming that argon gas has been introduced, adjust the DC power controller to the required power and turn on the power. Set the power to 200W and start pre-sputtering for 30 minutes to remove impurities from the target surface.

[0055] 6) After pre-sputtering, maintain the working pressure of argon gas in the cavity at 0.5 Pa, adjust the substrate bias voltage to 0 V, adjust the substrate temperature to 200 °C, remove the baffle above the substrate to start formal sputtering, and at the same time turn on the substrate 360° rotation switch and set the rotation speed to 80 sccm to maintain the uniformity of sputtering.

[0056] 7) The actual sputtering time is 2 hours. After the sputtering is completed, the film will be removed.

[0057] High-purity argon: conforms to national standard GB / T 10624-1995, with argon purity >99.999%, nitrogen content <5ppm, oxygen content <2ppm, hydrogen content <1ppm, total carbon content (calculated as methane) <2ppm, and moisture content <4ppm.

[0058] Comparative Example 1

[0059] Similar to Example 4, except that the substrate temperature is 100°C, the sputtering power is 100W, and the actual sputtering time is 40min, the film hardness becomes 40.5GPa and the elastic modulus becomes 582.3GPa.

[0060] Example 5

[0061] Similar to Example 4, except that the substrate temperature is 150°C, the sputtering power is 170W, and the actual sputtering time is 1 hour, the film hardness becomes 58.9 GPa and the elastic modulus becomes 790.2 GPa.

[0062] Example 6

[0063] Similar to Example 4, but with a sputtering power of 190W and a sputtering time of 1h, the film hardness becomes 68.5GPa and the elastic modulus becomes 905.3GPa.

[0064] Comparative Example 2

[0065] Similar to Example 4, but with a sputtering power of 130W, the film structure becomes amorphous, with a hardness of only 9.3 GPa and an elastic modulus of only 132.4 GPa. Compared to the present invention, the performance is reduced because a suitable sputtering power can enhance the adhesion between the film and the substrate, improve the density and uniformity of the film, and thus improve the mechanical properties such as the hardness and elastic modulus of the film.

[0066] Comparative Example 3

[0067] Similar to Example 1, except that the substrate temperature is 220°C, the grains of the film are too coarse, the hardness decreases to 30 GPa, and the elastic modulus decreases to 570 GPa.

Claims

1. A crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film with high modulus and hardness, characterized in that, Ti-Zr-Hf-Co-Ni-Cu are in equal atomic percentages, with the specific chemical composition being Ti 16.67 Zr 16.67 Hf 16.67 Co 16.67 Ni 16.67 Cu 16.67 ; The high modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film has an elastic modulus of 592-930.2 GPa and a hardness of 43-70.3 GPa, and the film has a single-phase crystalline structure.

2. The high modulus and high stiffness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film of claim 1, wherein, The high modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film has a nanocrystalline grain of 200-300 nm in the microstructure, the nanocrystalline grain is a B2 ordered phase (BCC structure), and the crystallinity is higher than 90%.

3. The method of producing a high modulus and high stiffness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film according to claim 1 or 2, characterized in that, The high modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film is prepared by an ultra-high vacuum direct-current magnetron sputtering method, and the crystallinity, elastic modulus and hardness of the film are adjusted by changing the substrate temperature and sputtering power; wherein the substrate temperature is 20-200 DEG C, and the sputtering power is 150 W-200 W.

4. The method for preparing high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin films according to claim 3, characterized in that, Specifically, the method comprises the following steps: S1: a single crystal silicon wafer is selected as a substrate, and the substrate is subjected to surface treatment, impurity removal and drying to obtain an impurity-removed substrate; S2: the impurity-removed substrate is placed in a mold with the polished surface facing downward, and is horizontally inserted into an ultra-high vacuum magnetron sputtering system with a baffle shielding the substrate; S3: an equal-atomic percentage TiZrHfCoNiCu alloy target material is fixed on a direct-current power supply; S4: The vacuum degree is pumped to 10 -5 Pa, high-purity argon is introduced, the flow rate of argon is 20-30sccm, the pressure in the cavity is kept at 0.2-0.5Pa, and glow cleaning is performed for 30-60min. S5: the argon gas is kept flowing, the sputtering power is adjusted to 150 W-200 W, and the target material is pre-sputtered for 30-60 min to remove the surface impurities on the target material; S6: after the pre-sputtering, the working gas pressure in the cavity of the ultra-high vacuum magnetron sputtering system is kept at 0.5-0.7 Pa, the argon gas flow rate is kept at 20-30 sccm, the substrate bias voltage is adjusted to 0 V, the substrate temperature is adjusted to 20-200 DEG C, the baffle above the substrate is removed to start formal sputtering, and the uniform sputtering is continuously performed for 30 min-2 h, and the film is cooled in the furnace to obtain the high modulus and hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory film.

5. The method for preparing a high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film according to claim 4, characterized in that, In S1, the size of the single crystal silicon wafer is 15 mm x 15 mm.

6. The method of claim 4, wherein the high modulus and high stiffness crystalline Ti-Zr-Hf-Co-Ni-Cu based high-entropy shape memory thin film is prepared by a method comprising: depositing a thin film of a Ti-Zr-Hf-Co-Ni-Cu based high-entropy alloy on a substrate; and annealing the thin film at a temperature of 400-600 °C for 1-10 hours. In S1, the single crystal silicon wafer is a single-side polished single crystal silicon wafer with 140-160 mu m SiO2 on the surface.

7. The method for preparing a high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film according to claim 4, characterized in that, In S1, the impurity removal is performed by first ultrasonicating with acetone for more than 30 min, then ultrasonicating with alcohol for more than 30 min, and finally washing with deionized water until the surface is clean.

8. The method for preparing a high-modulus and high-hardness crystalline Ti-Zr-Hf-Co-Ni-Cu high-entropy shape memory thin film according to claim 4, characterized in that, In S6, the method for continuously and uniformly sputtering is that a 360 DEG rotation switch of the substrate is opened, and the rotation speed is set to 50-80 sccm to keep the uniformity of sputtering.

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