A method for regulating the properties and thermal stability of CuZrAl metallic glass through melt phase transition

Abstract

The present invention belongs to the field of metallic glass and provides a method for regulating the performance and thermal stability of CuZrAl metallic glass by melt phase transition, comprising: taking each metal element according to the composition ratio of CuZrAl metallic glass, placing it in an induction melting chamber, ‑5 Pa~10 ‑4 Pa, and repeatedly smelting for 5 to 10 times under the protection of an inert atmosphere to obtain a CuZrAl alloy; ‑6 Pa~10 ‑5 Pa, inert atmosphere protection, heated to a temperature above the melting point, quenching temperature T q Cu is heated to 1473K~1573K 46 Zr 46 The Al8 melt was cooled at a rate of 10 4 K / s freezes into a metallic glass solid, which is obtained. LLST will cause more and more dispersed icosahedral atomic clusters in its structure, thereby improving the glass forming ability and thermal stability; before and after the occurrence of LLST in high-temperature melts, the structural origin that determines the mechanical properties changes, resulting in the hardness and elastic modulus of metallic glass changing with the quenching temperature T q The decrease shows a two-stage change with the LLST occurrence temperature as the turning point, first decreasing and then increasing.

Description

Technical Field

[0001] The present invention belongs to the field of metallic glass, and in particular relates to a method for regulating the performance and thermal stability of CuZrAl metallic glass through melt phase transition. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Metallic glass is attracting increasing attention due to its unique properties that differ from those of conventional crystalline metals. Currently, metallic glass is generally prepared through a rapid melt cooling process. During the preparation process, it undergoes three stages: a high-temperature melt, a supercooled liquid, and a glassy solid. The most critical properties of these stages are thermal stability and glass-forming ability. Generally, glass-forming ability can be enhanced through various means, including the addition of small amounts of elements, manipulation of casting parameters, or control of the melt structure.

[0004] The liquid-liquid structure transition (LLST) refers to the transition between two disordered structures of identical chemical composition and has long been a research hotspot in condensed matter physics. Numerous reports exist on LLST in metallic glass-forming systems, but most focus on the supercooled liquid region. The liquid-liquid structure transition (LLST) phenomenon, an anomalous structural transition behavior discovered in recent years in the high-temperature and supercooled liquid regions of metallic glass-forming systems, has yet to fully understand its effect on the solid properties of metallic glasses. Addressing this issue is urgent, as it aims to better understand the evolution of the liquid structure of metallic glasses and to more precisely control and predict their properties. Summary of the Invention

[0005] To address the above-mentioned issues, the present invention provides a method for regulating the performance and thermal stability of CuZrAl metallic glass through melt phase transition. The present invention found that the liquid-liquid structural transition behavior can significantly improve the thermal stability and glass-forming ability of CuZrAl metallic glass. In terms of mechanical properties, due to the change in the dominant structural origin, the hardness and modulus of the sample before and after the liquid-liquid structural transition change with T q The temperature rise shows a trend of first falling and then rising. Based on the above rule, the present invention selects the quenching temperature T q When the temperature is 1473K~1573K, the melt structure after the liquid-liquid structure transition in the high-temperature liquid phase zone is frozen into the metallic glass strips to form a metallic glass solid, which effectively improves the thermal stability, glass forming ability and mechanical properties of CuZrAl metallic glass.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention provides a method for regulating the properties and thermal stability of CuZrAl metallic glass through melt phase transformation, comprising:

[0008] According to the composition ratio of CuZrAl metallic glass, each metal element was taken and placed into the induction melting chamber. -5 Pa~10 -4 Pa, and repeatedly smelting 5 to 10 times under the protection of an inert atmosphere to obtain a CuZrAl alloy;

[0009] The CuZrAl alloy was heated to 10 -6 Pa~10 -5 Pa, inert atmosphere, heated to a temperature above the melting point, cooled by single roller chilling and stripping method, and then q When the temperature is 1473-1573K, the melt structure after the liquid-liquid structure transition in the high-temperature liquid phase region is frozen into the metallic glass strips to form a metallic glass solid.

[0010] Said properties include: glass forming ability, hardness and modulus;

[0011] The temperature above the melting point is 150 to 450 K higher than the melting point.

[0012] Different from improving the glass-forming ability by "adding a small amount of elements, controlling casting parameters or controlling the melt structure", the present invention proposes a method for improving the glass-forming ability and thermal stability of CuZrAl metallic glass. By using a single-roll chilling strip method, melt superheating and liquid-liquid structure transformation are combined, and the melt structure after the liquid-liquid structure transformation is frozen into the metallic glass solid, the glass-forming ability and thermal stability of CuZrAl metallic glass are significantly improved.

[0013] The present application also provides a method for improving the hardness and modulus of CuZrAl metallic glass, based on the hardness and modulus of the sample before and after the liquid-liquid structure transition with T q The temperature rise shows a trend of first falling and then rising. The present invention selects T q The temperature is 1523K~1573K to obtain CuZrAl metallic glass with excellent hardness and modulus and high thermal stability.

[0014] The second aspect of the present invention provides CuZrAl metallic glass prepared by the above method.

[0015] The third aspect of the present invention provides an application of liquid-liquid structural transition in improving the thermal stability and glass-forming ability of CuZrAl metallic glass.

[0016] A fourth aspect of the present invention provides the application of liquid-liquid structural transition in improving the hardness and modulus of CuZrAl metallic glass.

[0017] Beneficial effects of the present invention

[0018] (1) Taking CuZrAl metallic glass as the research object, the liquid-liquid structural transition behavior of its high-temperature liquid phase region was discovered through dynamic viscosity. The melt structure after the liquid-liquid structural transition was frozen into the metallic glass strip by using the single-roller quenching strip method, and its influence on various properties of the metallic glass such as thermal stability, glass forming ability and mechanical properties was analyzed, and the structural origin that led to different property change trends before and after the structural transition was explored. The experimental results show that the liquid-liquid structural transition behavior will lead to a significant improvement in the thermal stability and glass forming ability of CuZrAl metallic glass. In terms of mechanical properties, due to the change in the dominant structural origin, the hardness and modulus of the sample before and after the liquid-liquid structural transition change with T q The temperature rise shows a trend of first decreasing and then increasing. This conclusion provides new ideas for improving the performance of metallic glass by regulating the melt structure, and has a promoting effect on the development of high-performance metallic glass materials.

[0019] (2) Although the process of changing material properties by controlling the quenching temperature or holding time is relatively common, the properties of metallic glasses with different compositions are affected differently by the quenching temperature and holding time. Therefore, it is difficult to find a relatively general rule to predict the properties of metallic glasses prepared under different quenching and holding conditions. This paper analyzes the influence of quenching temperature on the properties of CuZrAl metallic glasses with LLST phenomenon and summarizes the different mechanisms and performance control methods of the influence of quenching temperature on the properties of metallic glasses before and after LLST occurs.

[0020] Normally, when preparing metallic glass ribbons, the quenching temperature is generally selected to be 50-200K above the melting point, taking into account equipment conditions and oxidation issues. The samples of the present invention achieve a high superheat of 150K above the melting point to a maximum of 450K by installing an infrared temperature measuring device on the upper part of the single-roll quenching equipment and utilizing the high vacuum degree of the equipment, and obtain the performance of metallic glass samples at different superheats. The present invention discovered different laws of the influence of quenching temperature on the performance of CuZrAl metallic glass before and after the LLST phenomenon, providing a new method for regulating the hardness, modulus, etc. of metallic glass by higher quenching temperature, and also providing a reference law for the influence of quenching and insulation conditions on the performance of other metallic glasses with LLST phenomenon.

[0021] (3) The preparation method of the present invention is simple, practical, and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 Schematic diagram of a single-roller chilling and stripping device.

[0024] Figure 2 Cu 46 Zr 46 Equilibrium viscosity and DSC cooling curve of Al8 melt during cooling process.

[0025] Figure 3 Different T q Cu prepared by spinning at 46 Zr 46 XRD curve of Al8 metallic glass ribbon.

[0026] Figure 4 With different T q (a) DSC curve of Cu46Zr46Al8 metallic glass ribbon at different temperatures, and (b) values ​​of ΔT and γ parameters that characterize the glass-forming ability.

[0027] Figure 5 With different T q Temperature of Cu 46 Zr 46 (a) Crystallization peak tip temperature T of Al8 metallic glass ribbon p , (b) Crystallization activation energy E x .

[0028] Figure 6 T q High-resolution transmission electron microscopy images and selected area electron diffraction results of metallic glass strips at (a) 1323K, (b) 1423K, and (c) 1523K, where the yellow dotted square area represents the localized ordered structure, and the yellow solid circular area represents the element segregation area.

[0029] Figure 7 Cu 46 Zr 46 Analysis of the order of Al8 metallic glass HRTEM images. Figure (a) shows the method of dividing the square unit map. Figures (b)-(d) are T q It is a two-dimensional diagram of the ordered structure of 1323K, 1423K and 1523K strips. Figure (e) shows the percentage of disordered units (red part) and ordered units (blue part) in the total number of graphic units.

[0030] Figure 8 Cu 46 Zr 46The hardness and modulus calculated by nanoindentation of Al8 metallic glass and the relationship between the quenching temperature T q relationship.

[0031] Figure 9 (a)Cu 46 Zr 46 Compressive stress-strain curve of Al8 metallic glass microcolumns. The insets are the microcolumn morphology before compression and the magnified image of the red dotted box area; (b) Cu 46 Zr 46 Relationship between compression height and compression strain rate during compression of Al8 metallic glass micropillars.

[0032] Figure 10 Cu 46 Zr 46 Shear band expansion during compression of Al8 metallic glass micropillars, ad is micropillar A; eh is micropillar B; il is micropillar C. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0034] A method for regulating the properties and thermal stability of CuZrAl metallic glass through melt phase transition, comprising:

[0035] According to the composition ratio of CuZrAl metallic glass, each metal element was taken and placed into the induction melting chamber. -5 Pa~10 -4 Pa, and repeatedly smelting 5 to 10 times under the protection of an inert atmosphere to obtain a CuZrAl alloy;

[0036] The CuZrAl alloy was heated to 10 -6 Pa~10 -5 Pa, inert atmosphere, heated to a temperature above the melting point, cooled by single roller chilling and stripping method, and then q When the temperature is 1473K~1573K, the melt structure after the liquid-liquid structure transition in the high-temperature liquid phase region is frozen into the metallic glass strip to form a metallic glass solid.

[0037] Said properties include: glass forming ability, hardness and modulus;

[0038] The temperature above the melting point is 150 to 450 K higher than the melting point.

[0039] In the present invention, Cu 46 Zr 46The LLST temperature of Al8 metallic glass is around 1450K.

[0040] In some embodiments, the quenching temperature T q It is 1473K, 1523K or 1573K.

[0041] In some embodiments, the inert gas atmosphere is argon.

[0042] In some embodiments, CuZrAl metallic glass is Cu 46 Zr 46 Al8 metallic glass.

[0043] In some embodiments, the specific cooling method is to use a single-roller chilling and stripping device for cooling.

[0044] In some embodiments, the specific cooling method is to spray the melt onto the surface of a rotating copper roller using a pressure difference, and under the action of centrifugal force, the metal strip is separated from the surface of the copper roller.

[0045] In some embodiments, the rotation speed of the copper roller is 2500-2600 r / min.

[0046] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0047] In the following examples, the differential scanning calorimeter is a DSC-404C model produced by NETZSCH GmbH, Germany, with a supported temperature range of 0 to 1500° C. and a maximum heating rate of 50 K / min. The crucible is made of alumina.

[0048] The X-ray diffraction (XRD) instrument was an AXS D8 ADVANCE X-ray diffractometer from Bruker, Germany, using Cu target Kα monochromatic light, with a scanning angle range of 20 to 80 degrees and a scanning speed of 10 degrees / min.

[0049] The scanning electron microscope (SEM) used was a field emission JSM-708OF, and this was used to analyze the structure and element distribution at the interface between the sample and the crucible after the viscosity test.

[0050] The high-resolution transmission electron microscope (HRTEM) was a Titan 80-300 model from FEI.

[0051] The nanoindentation equipment is the Tl980 nanomechanical testing system produced by Bruker, Germany.

[0052] The strength and plasticity of materials are typically measured through tensile or compression tests. However, metallic glass ribbons are only a dozen microns thick, making macroscopic compression or tensile tests difficult. This paper uses FIB cutting to create a 2μm diameter cylinder on the surface of the metallic glass ribbon. In situ micro-column compression tests are then performed on this cylinder using a SEM microscope to determine the material's strength and plasticity.

[0053] Example 1 Preparation of metallic glass ribbon samples

[0054] The preparation of metallic glass ribbon samples mainly includes two steps: alloy melting and rapid cooling and ribbon throwing.

[0055] The alloy is prepared by arc melting. High-purity metal elements are placed in the induction melting chamber according to the composition ratio, and the chamber is evacuated to 10 by a mechanical vacuum pump and a molecular pump. -4 Pa, and then high-purity argon is introduced to prevent oxidation of the sample. To ensure uniform melting of the sample, 5-10 repeated meltings are performed to finally obtain alloy button ingots of corresponding composition, each weighing about 25g.

[0056] After the alloy button ingot is prepared, the metallic glass ribbon is obtained by a single roller chilling stripping device. The structure is as follows: Figure 1 As shown. The button alloy ingot obtained by arc melting is cut into 5-7g small pieces by wire cutting and placed in a quartz test tube. When vacuuming, first use a mechanical pump to draw a low vacuum, and then use a molecular pump to draw the vacuum degree to 10 -5 Pa, and then high-purity argon is introduced. The alloy block is heated to a specified temperature above its melting point by induction heating (temperature is monitored by infrared thermometry). The melt is then ejected onto the surface of a high-speed rotating copper roller using a pressure differential, achieving extremely high cooling rates. Under the action of centrifugal force, the metal strip prepared by rapid cooling will detach from the copper roller surface, ultimately resulting in a metallic glass strip with an amorphous structure.

[0057] To further explore the effect of LLST on Cu 46 Zr 46 The influence of Al8 metallic glass melt structure evolution and solid properties on different quenching temperatures T q (1273K, 1323K, 1373K, 1423K, 1473K, 1523K, 1573K) 46 Zr 46 The Al8 melt was cooled at an ultra-high cooling rate (the speed of the copper rollers was 2500 r / min and the cooling rate was about 10 4 K / s) is frozen into a metallic glass solid, and its thermal stability, crystallization characteristics, mechanical properties and other aspects are analyzed. The laws of how the melt thermal history and LLST affect the properties of metallic glass, as well as the structural origin and regulation methods are explored.

[0058] Example 2 Liquid-Liquid Structure Transition Phenomenon in CuZrAl Alloy Melt

[0059] Figure 2 Cu 46 Zr 46 The change of equilibrium viscosity of Al8 alloy melt with decreasing temperature and DSC curve of cooling process. 46 Zr 46 The equilibrium viscosity of Al8 alloy was measured during the cooling process after the temperature was raised to 1700K (550K above the liquidus temperature). The viscosity data obtained from the experiment ranged from 1 to 10 mPa·s, which is consistent with the viscosity data of CuTiZrNi alloy melt reported by previous researchers. Under normal circumstances, the shear friction between the atoms in the melt will increase during the cooling process, and the viscosity will continue to increase. However, in Cu 46 Zr 46 The viscosity data of Al8 melt showed that in the temperature range of 1600K to 1450K, the viscosity value gradually increased with decreasing temperature, but at 1450K, the viscosity data showed a significant decrease, and the decrease range far exceeded the experimental error range of viscosity measurement. Therefore, it can be considered that Cu 46 Zr 46 This unusual drop in viscosity in Al8 melts is essentially a temperature-induced kinetic change. Researchers have observed similar phenomena in pure metal liquids such as Bi, Sb, Sn, and In, as well as simple binary alloy liquids such as Al-Cu and Sn-Bi, and have interpreted this phenomenon as a transition between two liquid structures.

[0060] In order to further study Cu 46 Zr 46 Thermodynamic response of LLST phenomenon in Al8 alloy melt, Figure 2 The DSC curves in the temperature range of 1200K to 1600K are given in . Figure 2 Three obvious exothermic peaks can be seen in the figure. The sharp exothermic peaks at 1240K and 1300K are close to the liquidus position of the alloy system. It can be considered that these two peaks correspond to Cu 46 Zr 46 Solidification peak of Al8 alloy. However, the exothermic peak at around 1450K is far from the liquidus temperature, but it is consistent with the temperature of abnormal viscosity decrease, which can be used as thermodynamic evidence of LLST.

[0061] Example 3 Microstructure of CuZrAl Metallic Glass

[0062] The present invention is different from q Cu was prepared at46 Zr 46 Al8 metallic glass strips, in order to verify its amorphous structure, X-ray diffraction experiments were carried out. Due to the structural characteristics of amorphous with long-range disorder and short-range order, it appears as a broad scattering bun peak in the XRD curve, and does not produce sharp diffraction peaks similar to crystal structures. q The X-ray diffraction results of metallic glass strips prepared at temperature are as follows Figure 3 As shown. It can be found that the strips prepared at different quenching temperatures do not have sharp peaks representing the crystal phase, and show an obvious diffuse scattering peak at 2θ = 38°. Therefore, it can be considered that the seven prepared strips with different T q The metallic glass strips all show an amorphous structure.

[0063] Example 4 with different T q Thermodynamic properties of metallic glass ribbons

[0064] Figure 4 For different T q Cu prepared at 46 Zr 46 DSC curve of Al8 metallic glass ribbon. Related thermodynamic parameters T of the ribbon sample g ,T x ,ΔT(ΔT=T x -T g ), and the γ coefficient (γ=T x / (T g +T L ),T L is the liquidus temperature of the system) as shown in Table 4-1. From the data in the table, we can see that when T q When the crystallization temperature T of the metallic glass ribbon increases x Also changes will occur, especially when T q When the temperature is greater than 1423K, the crystallization temperature of the ribbon sample increases from 765.56K to 775.38K, which is a very obvious change. In addition, the glass transition temperature T g Slightly reduced. q In the higher regions (1473K, 1523K and 1573K), the thermodynamic behavior related to the glass transition becomes less obvious. A large number of studies have confirmed that even if the glass phase contains a small amount of crystalline phase, a clear glass transition region will appear. These results show that, excluding the influence of the crystalline phase, at high T q The phenomenon that the glass transition region becomes less obvious is caused by the change of the disordered amorphous structure in the metallic glass solid.

[0065] Table 1 has different T q Cu 46 Zr 46Related thermodynamic parameters T in Al8 metallic glass ribbons g ,T x ,ΔT, and γ values

[0066]

[0067] Related research shows that the Zr-based multi-component metallic glass structure contains medium-range ordered icosahedral atomic clusters, which have high metastability. During the heating process, these medium-range ordered clusters can improve the crystallization resistance of the metallic glass, leading to the appearance of the glass transition region. Since the cooling rate of the metallic glass ribbon prepared by the single-roll chilling strip device can reach 10 4 K / s, the atomic structure of the metallic glass ribbon prepared in this way is closely related to its corresponding high-temperature melt. 46 Zr 46 In the Al8 metallic glass system, when the melt temperature is high, the polyhedral atomic configuration in the melt is more in a low-coordination state, and it is difficult to form a medium-range ordered atomic structure. As the melt temperature decreases, the content of high-coordination icosahedral atomic clusters with high stability increases, resulting in the gradual emergence of the glass transition region. Through viscosity experiments, it was found that Cu 46 Zr 46 Al8 alloy melt undergoes reversible LLST behavior near 1423K, which further increases the content of icosahedral structure in the melt and reduces its interconnection degree, making it more dispersed, resulting in Figure 4 (a) T q The glass transition behavior is very obvious at 1423K.

[0068] It is generally believed that there is a positive correlation between the width of the supercooled liquid phase (ΔT) and γ and the glass forming ability (GFA). 46 Zr 46 The width of supercooled liquid region and γ coefficient of Al8 metallic glass ribbon and T q The relationship between temperature Figure 4 As shown in (b). Figure 4 It can be seen that the two parameters ΔT and γ vary with T q The temperature variation trends are basically the same, indicating that the 46 Zr 46 In Al8 metallic glass, these two parameters are relatively reliable in characterizing its glass forming ability. q As the temperature decreases, its glass forming ability gradually decreases. However, with 1423K as the dividing point, the two parameters ΔT and γ decrease with T qThe temperature change suddenly becomes gentle, and at 1373 K, both parameters show a sudden increase. For the same glass-forming system, its glass-forming ability is closely related to its structure, and the turning point temperature of 1423 K is consistent with the Cu2O3 observed by melt viscosity data. 46 Zr 46 The occurrence temperature of LLST phenomenon in Al8 alloy is very close to 1450K. Therefore, it can be considered that the LLST phenomenon in the melt has a great influence on the Cu 46 Zr 46 The glass forming ability of Al8 metallic glass is significantly affected by the melt temperature, and there are certain differences in the influence of melt temperature on the glass forming ability before and after LLST occurs, indicating that the structural origin of the melt that plays a decisive role in the glass forming ability has changed.

[0069] The crystallization behavior of metallic glasses is closely related to their amorphous structure. Figure 5 is the temperature at the crystallization peak T p and crystallization activation energy E x With T q It can be found that as T q As the temperature rises, Cu 46 Zr 46 The crystallization peak temperature and activation energy of Al8 metallic glass exhibit a two-stage transition, with a turning point near 1423 K, which closely matches the onset temperature of the LLST phenomenon. This suggests that LLST in the melt alters the amorphous structure of the prepared metallic glass ribbons and significantly affects their crystallization behavior.

[0070] Example 5T q Structural origins of properties affecting CuZrAl metallic glass

[0071] The structure of metal alloy melts is very complex and closely related to temperature. Many previous studies have shown that as the metal melt heats up, its atomic structure gradually tends to be uniform as the superheat increases, and the metastable localized ordered atomic clusters and element segregation clusters in the structure gradually dissipate as the temperature rises. When the melt rises to a critical temperature (generally 1.3-1.4T), the m , T m is the melting temperature of the alloy), the metastable localized ordered atomic clusters completely disappear. The presence of these atomic clusters will lead to local structural inhomogeneities in the melt. At the same time, they will also serve as nucleation sites during the crystallization process of the melt, greatly reducing the energy required for the crystallization of the alloy melt. Therefore, for the metallic glass system, its glass forming ability is closely related to its corresponding melt state. Cu 46 Zr 46 Melting temperature T of Al8 alloy mThe critical temperature is 1120.73K, and the critical temperature is about 1500K. When the melt is at 1573K, the melt is in a completely homogeneous state, and there are almost no metastable localized ordered atomic clusters in the structure. Therefore, T q The crystallization process of metallic glass ribbons at 1573K requires a larger activation energy and a longer atomic diffusion distance, and the glass forming ability is stronger. When the melt temperature decreases, although the content of icosahedral clusters in the melt increases slightly, they tend to connect with each other and grow, eventually evolving into crystal nuclei. At the same time, the metastable localized ordered atomic clusters precipitated during the cooling process will also reduce the energy required for crystallization, ultimately leading to a gradual decrease in the glass forming ability of the metallic glass ribbon. For T q The LLST behavior has already occurred during the cooling process of the melt. The more and more dispersed icosahedral atomic clusters in the melt structure caused by LLST can greatly improve the glass forming ability of the system. q When the temperature is 1373K, Cu 46 Zr 46 The glass forming ability of Al8 metallic glass will suddenly increase. As the melt temperature continues to decrease, the gradually growing local ordered clusters will once again dominate the competition with various structures that affect the glass forming ability, resulting in a low T q Temperature (1323K, 1273K) the ability of metallic glass strips to resist crystallization becomes weaker.

[0072] To find T q The organizational transformation in the metallic glass strip structure caused by different q HRTEM images were taken for the strip samples at 1323K, 1423K, and 1523K, as shown in Figure 5 As shown, observe the changes in its microstructure. Figure 6 The illustrations in the upper right corner of (a), (b) and (c) are the selected area electron diffraction (SAED) results. q The results at different temperatures are all shown as a halo without bright spots, indicating that its structure is amorphous. Figure 6 As can be seen in (c), T q At 1523K, the strip sample has an almost completely uniform structure, and there are no local ordered clusters and element segregation in the structure. q When it drops to 1423K, Figure 6As shown in (b), the element segregation area in the yellow solid circle and the quasi-crystalline ordered structure in the yellow dotted box area can be observed in the HRTEM image. When the melt temperature continues to decrease, these clusters in the melt will continue to precipitate and grow, and the content and size of these structures in the resulting metallic glass ribbon will continue to increase, as shown in Figure 2. Figure 6 As shown in (a).

[0073] The content and distribution of the quasi-crystalline atomic ordered structure can be expressed by the atomic order. In order to more accurately calculate the atomic order in the structure and to express it intuitively, we divide the HRTEM image into 14×14 small image units, each with a scale of 1.995×1.995nm. 2 . Using the Autocorrelation function (ACF) in Digital Micrograph software, a quantitative estimate of the atomic arrangement was obtained, such as Figure 7 As shown in (b)-(d). The algorithm considers images with clear stripes of atoms as ordered structures (crystal-like structures) and surrounds the images with red rectangles, and considers images with disordered atomic arrangements as disordered structures, as shown in (b)-(d). Figure 7 As shown in (a). The ordered image units in the HRTEM image are marked, and the percentage of the ordered structure image in the total image is calculated to obtain the percentage related to the degree of structural order, as shown in Figure 7 As shown in (e). According to the results of atomic order analysis, T q The decrease in leads to an increase in the proportion of quasi-crystalline structures, which is 5.61% at 1523 K, 13.27% at 1423 K, and 22.45% at 1323 K. As mentioned above, the localized element segregation structures and larger atomic ordered clusters that appear more frequently in low-temperature melts are more likely to evolve into quasi-crystalline structures. Figure 4 (b) Three Ts q The glass forming ability at temperatures of 10 ...

[0074] Example 6 with different T q Mechanical properties of metallic glass ribbons

[0075] Since metallic glass does not have atomic structural defects such as dislocations and lattice distortions, it has many excellent mechanical properties that are different from crystalline metal materials, such as high hardness, strength, fracture toughness, etc. Mechanical properties are a macroscopic manifestation of material properties, but in essence they still depend on the microstructure of the material. Rapidly cooled metallic glass inherits different structures from the melt, and its mechanical properties also have certain differences. The LLST that occurs in the melt will cause the melt structure to change and ultimately affect the thermal stability, glass forming ability and other properties of the metallic glass. However, there are still few studies on the effect of LLST on the mechanical properties of metallic glass. In order to reveal the effects of melt thermal history and LLST phenomenon on Cu 46 Zr 46 Effect of hardness and modulus of Al8 metallic glass on different T q Nanoindentation mechanical properties of metallic glass strip samples were tested. To reduce the influence of size effect on hardness results, a large load of 3000μN was used. The final pressure-depth curve, hardness and modulus were calculated using the Olive-Pharr method. The results are shown in the figure below. Figure 8 shown.

[0076] Depend on Figure 8 It can be seen that when the strip sample T q When the temperature decreases, its H and M are critical at 1423K, and show a trend of first decreasing and then increasing. q At 1573K, the hardness H and modulus M of the strip sample reach their maximum values, which are 8.6GPa and 121GPa respectively. q It is in a lower state when it is in the range of 1373-1473K. q When the temperature is 1423K, both H and M show an abnormal increase, and the temperature of this abnormal increase is very close to the temperature at which LLST occurs. When the researchers explored the mechanical properties of metallic glass, they found that increasing the quenching temperature of Cu-based and Zr-based metallic glasses can significantly improve their hardness and modulus. As the melt temperature increases, the structural uniformity of the melt increases, and its spatial heterogeneity is also different from that of the low-temperature melt. This difference will also affect the hardness and modulus of the CuZrAl metallic glass system. However, the quenching temperature T q The influence of Cu on hardness and modulus is not consistent over the entire temperature range, and there is a turning point with a critical temperature close to the LLST occurrence temperature. 46 Zr 46 When the melt temperature of Al8 alloy is higher than 1473K, the q As the temperature rises, the hardness and modulus of the quenched metallic glass ribbon will gradually increase. 46 Zr 46 When the melt temperature of Al8 alloy is less than 1373K, as T qAs the temperature rises, the hardness and modulus of the metallic glass ribbon obtained by quenching will gradually decrease. Considering that the critical temperature of 1423K is very close to the LLST temperature of 1450K, and LLST will cause discontinuous changes in the melt structure, it can be considered that the structure of the melt before and after LLST is quite different, and the origin of the internal structure that determines the mechanical properties such as hardness and modulus is different, which ultimately leads to T q The influence of temperature on the hardness and modulus of metallic glass is different. When the melt is cooled from a high temperature state to 1423K, LLST occurs. At this time, the icosahedral structures in the melt structure become more dispersed instead of interconnected as the temperature decreases. This phenomenon of large atomic clusters splitting will make the melt more uniform to a certain extent, thereby reducing spatial heterogeneity, and ultimately causing the hardness and modulus of the metallic glass to increase slightly. In the low temperature region (T q When the melt is not sufficiently superheated (≤1373K), ordered atomic clusters in the structure gradually appear and grow as the temperature decreases. When the melt is quenched, these localized ordered atomic clusters, large or small, are retained in the metallic glass solid, and some clusters even gradually grow to form quasi-crystalline structures. The distribution of these quasi-crystalline structures has a certain strengthening effect on the amorphous matrix, thereby improving the hardness and modulus of the metallic glass to a certain extent.

[0077] Since the prepared metallic glass sample is a strip with a thickness of only 20 μm, it is impossible to obtain the stress-strain curve of the sample through macro compression or tension experiments. In the present invention, micro cylinders with a diameter of 2 μm and a height of 4 μm were prepared on the surface of the strip sample by the focused ion beam (FIB) sample preparation method. The morphology of the micro cylinder is as follows Figure 9 As shown in the illustration in (a), the compressive stress-strain curve is Figure 9 As shown in (a). From the compression test results, T q The three metallic glass micropillars (labeled as micropillars A, B, and C) at temperatures of 1273K, 1423K, and 1523K showed no obvious yielding phenomenon and showed obvious brittleness. Their strengths were 2660.5MPa, 2755.4MPa, and 2802.2MPa, respectively, showing that the strength of the three metallic glass micropillars increased with T. q Although all three micropillars exhibit brittle failure behavior, their plasticity still differs to a certain extent. Figure 9The magnified image of the red dashed box in (a) shows that micropillar A exhibits multiple displacement bursts during compression deformation. This phenomenon is believed to be related to the activation of a single shear band during the deformation of the metallic glass. As mentioned above, the plastic deformation of metallic glass is driven by its shear bands, and regions with high free volume content can hinder the expansion of shear bands and promote their splitting, thereby enhancing the plasticity of the metallic glass to a certain extent. The multiple yield steps in micropillar A represent the activation of multiple shear bands, indicating that it still has a certain degree of plastic deformation capacity. Figure 9 (b) shows the relationship between the compression strain rate and compression height of the three micropillars A, B, and C. Each large fluctuation area corresponds to a displacement burst step on the stress-strain curve. The figure clearly shows the number of displacement burst steps for each micropillar during the compression process.

[0078] Figure 10 The shear band expansion of the three micropillars A, B, and C during the compression process is shown. The area pointed by the yellow arrow is the shear band that has penetrated the micropillar. Figure 10 (d), (h), and (i) show the morphologies of micropillars A, B, and C after compression testing, respectively. Micropillar A experiences a greater vertical strain before the appearance of a shear band through the micropillar, indicating greater plasticity. During the compression test, even after a single shear band penetrates the micropillar, its cross-section retains a certain degree of cohesion, preventing destructive fracture.

[0079] The mechanical properties of metallic glass are determined by many factors, including the bonding strength of its atomic bonds, the free volume content, and the atomic structure. The free volume has an important influence on the plastic behavior of metallic glass. Related studies have shown that in Cu-based and Zr-based metallic glass alloy systems, a lower melting temperature will lead to a higher free volume content, which will become the location of the shear band branch, limit the extension of the main shear band, and improve the plasticity of the metallic glass. However, this rule does not apply to La-based alloys, where an increase in the melt temperature will reduce the free volume content. For Cu 46 Zr 46 Al8 alloy, lower T q This will result in a higher free volume and crystal-like structure content. These atomic cluster structures will provide shear band branching sites to prevent brittle fracture. q As the size increases, the free volume and the locally ordered quasi-crystal structure gradually dissolve, and the degree of melt homogenization increases, which eventually leads to the brittle fracture of micropillar C when compressed at room temperature.

[0080] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for regulating the properties and thermal stability of CuZrAl metallic glass by melt phase transition, characterized in that: include: According to the composition ratio of CuZrAl metallic glass, each metal element was taken and placed into the induction melting chamber. -5 Pa~10 -4 Pa, and repeated melting 5 to 10 times under the protection of inert gas atmosphere to obtain CuZrAl alloy; The CuZrAl alloy was heated to 10 -6 Pa~10 -5 Pa, inert atmosphere protection, heated to a temperature above the melting point, using a single roller chilling strip method to cool, at quenching temperature T q When the temperature is 1473 K to 1573 K, the melt structure before and after the liquid-liquid structure transition in the high-temperature liquid phase region is frozen into the metallic glass strip to form a metallic glass solid; the CuZrAl metallic glass is Cu 46 Zr 46 Al8 metallic glass; The cooling rate is 10 4 K / s; Said properties include: glass forming ability, hardness and modulus; The temperature above the melting point is 150-450 K higher than the melting point.

2. The method for regulating the properties and thermal stability of CuZrAl metallic glass by melt phase transition according to claim 1, wherein: The temperature of LLST is 1450 K.

3. The method for regulating the properties and thermal stability of CuZrAl metallic glass by melt phase transition according to claim 1, wherein: The quenching temperature T q Selected from 1473 K, 1523 K or 1573 K.

4. The method for regulating the properties and thermal stability of CuZrAl metallic glass by melt phase transition according to claim 1, wherein: The inert gas atmosphere is argon.

5. The method for regulating the properties and thermal stability of CuZrAl metallic glass by melt phase transition according to claim 1, wherein: The specific cooling method is to use a single-roller chilling and stripping device for cooling.

6. The method for regulating the properties and thermal stability of CuZrAl metallic glass by melt phase transition according to claim 1, wherein: The specific cooling method is to spray the melt onto the surface of a rotating copper roller using a pressure difference, and under the action of centrifugal force, the metal strip is separated from the surface of the copper roller to obtain the product.

7. The method for regulating the properties and thermal stability of CuZrAl metallic glass by melt phase transition according to claim 1, wherein: The rotation speed of the copper roller is 2500~2600 r / min.

8. CuZrAl metallic glass prepared by the method according to any one of claims 1 to 7.

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