A method of re-toughening a metallic glass

Abstract

The application provides a method for re-toughening metal glass, and relates to the technical field of mechanical property improvement of amorphous alloy, and comprises the following steps: performing current treatment on the relaxed state metal glass, heating the relaxed state metal glass to a first set temperature, and then performing quenching treatment; wherein the first set temperature is lower than the glass transition temperature Tg of the metal glass. It should be noted that the current treatment is performed on the relaxed state (aged state) metal glass to rapidly heat the metal glass to a higher temperature, at this time, the memory effect can be activated, the free volume content in the metal glass is increased to a certain extent, the energy state of the metal glass is improved, and then the increased free volume is retained through rapid cooling by quenching, so that the aging of the metal glass is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of improving the mechanical properties of metallic glasses, and particularly relates to a rejuvenation method of metallic glasses. BACKGROUND

[0002] Metallic glasses, also known as amorphous alloys, have attracted extensive attention due to their excellent mechanical properties, including extremely high strength, high elastic limit, and excellent friction and wear resistance, and have been widely used in many fields such as electronics, aviation, aerospace, medical devices, and microelectronics.

[0003] Since metallic glasses are obtained by rapidly cooling molten liquid, there will be certain residual stress inside, so annealing treatment must be performed below the glass transition temperature (Tg) before the metallic glass product is used to eliminate residual stress. However, annealing treatment will cause the metallic glass to age, i.e. relaxation (a process of reducing energy state). Aging easily leads to embrittlement of the metallic glass, which seriously hinders its practical application as a structural material. Therefore, in order to realize the reuse of aged metallic glasses, a new method for rejuvenating aged metallic glasses is urgently needed, which will greatly promote the large-scale application of metallic glasses.

[0004] Rejuvenation, also known as rejuvenation, has been proven to be an effective method to solve the above problems. Studies have shown that plastic deformation, elastic loading, irradiation, low-temperature thermal cycling, and other methods can rejuvenate metallic glasses. However, these methods are mainly suitable for as-cast metallic glasses, and are not suitable for rejuvenation of aged metallic glasses. However, in actual application of metallic glasses, annealed and aged metallic glasses are used rather than as-cast metallic glasses. Therefore, it is crucial to rejuvenate aged metallic glasses. The prior art discloses rejuvenating aged metallic glasses by annealing treatment, thereby restoring the ductility (and toughness) of annealed and aged metallic glasses. However, there are the following problems when rejuvenating aged metallic glasses by annealing treatment: the heating rate of traditional annealing furnaces is slow and there is a significant size effect, and when heating large samples, the temperature distribution is uneven, the outside temperature quickly reaches the rejuvenation temperature, while the inside needs a long time to reach the rejuvenation temperature, and since the outside is exposed to high temperature for a long time, it is inevitable that rejuvenation will occur again, resulting in poor rejuvenation effect of the metallic glass, and further resulting in poor rejuvenation effect of the metallic glass. SUMMARY

[0005] Therefore, the present application provides a rejuvenation method of metallic glasses, which can solve the problem of poor rejuvenation effect of metallic glasses in the prior art.

[0006] To solve the above problems, the application provides a method for re-toughening of metallic glass, comprising the following steps:

[0007] The current is passed through the metallic glass in relaxation state to heat the metallic glass in relaxation state to a first set temperature, and then quenching treatment is performed;

[0008] The first set temperature is lower than the glass transition temperature Tg of the metallic glass.

[0009] Further, the first set temperature is 0.93-0.96Tg.

[0010] Further, before the step of passing current through the metallic glass in relaxation state, the method further comprises:

[0011] The current is passed through the metallic glass in casting state to heat the metallic glass in casting state to a second set temperature, thereby obtaining the metallic glass in relaxation state.

[0012] The second set temperature is 0.8-0.85Tg.

[0013] Further, the diameter of the metallic glass in casting state is 2-4mm, and the length is 20-24mm.

[0014] Further, in the step of passing current through the metallic glass in casting state, the current is 12-18A, and the time is 4.5-5.5h.

[0015] Further, in the step of passing current through the metallic glass in relaxation state, the current is 18-27A, and the time is 20-60s.

[0016] Further, before the step of passing current through the metallic glass in casting state, the method further comprises: performing differential scanning calorimetry analysis on the metallic glass in casting state to obtain the relaxation enthalpy ΔH1 of the metallic glass in casting state.

[0017] Further, after the step of passing current through the metallic glass in casting state, the method further comprises: performing differential scanning calorimetry analysis on the metallic glass in relaxation state to obtain the relaxation enthalpy ΔH2 of the metallic glass in relaxation state.

[0018] ΔH1>ΔH2.

[0019] Further, after the quenching treatment, the method further comprises: performing differential scanning calorimetry analysis on the metallic glass after quenching treatment to obtain the relaxation enthalpy ΔH3 of the metallic glass after quenching treatment.

[0020] ΔH3>ΔH2.

[0021] Preferably, ΔH3 = 20% ΔH1 - 40% ΔH1.

[0022] The metal glass re-toughening method has the following beneficial effects:

[0023] 1. The metal glass re-toughening method comprises the following steps: current treatment is performed on a relaxed metal glass, the relaxed metal glass is heated to a first set temperature, and then quenching treatment is performed; wherein the first set temperature is lower than the glass transition temperature Tg of the metal glass. It should be noted that the relaxed (aged) metal glass is rapidly heated to a higher temperature by current treatment, at which time the memory effect can be activated, the free volume content in the metal glass is increased to a certain extent, the energy state of the metal glass is improved, and then the increased free volume is retained by rapid cooling through quenching, thereby realizing the rejuvenation of the aged metal glass; wherein the heating method is different from the traditional external heat conduction (such as furnace heating), and when the current passes through the internal resistance of the metal glass sample, heat (Joule heat) is generated, which does not need to be transmitted from the surface to the interior through heat conduction, thus avoiding the temperature lag problem caused by heat conduction delay in traditional heating, and greatly shortening the heating time; and the Joule heat is generated synchronously in each region of the metal glass sample, so that the temperature distribution is more uniform from the beginning, the temperature difference caused by heat conduction is reduced, and the size effect can be minimized even in large-size or complex-geometry samples.

[0024] 2. Further, by current treatment on the as-cast metal glass, the sample temperature is raised under the action of the resistance, which promotes the annihilation of free volume in the metal glass, thereby reducing the energy state of the metal glass and causing the metal glass to age; the current treatment has rapid heating, which further improves the re-toughening efficiency of the metal glass, and also releases the residual stress in the metal glass. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. The drawings in the following description are only exemplary, and those skilled in the art can also obtain other implementation drawings according to the provided drawings without creative labor.

[0026] Figure 1 Fig. 1 is a schematic diagram of current treatment in the metal glass re-toughening method of the present application and an energy change diagram in the prior art re-toughening method;

[0027] Figure 2In the middle: (a) and (b) are DSC curves and energy evolution diagrams of cast metallic glasses, aged metallic glasses and young metallic glasses of different sizes, respectively;

[0028] Figure 3 In the middle: (a)-(d) are the XRD curves and corresponding transmission electron microscope images of cast metallic glass, aged metallic glass and aged metallic glass, respectively;

[0029] Figure 4 In the middle: (a), (b), and (c) are the hardness change curve, plastic strain curve, and compressive stress-strain curve of cast metallic glass, aged metallic glass, and aged metallic glass, respectively;

[0030] Figure 5 Nanoindentation creep behavior of cast metallic glass, aged metallic glass and aged metallic glass;

[0031] Figure 6 In the middle: (a)-(c) are the DSC curves of the aging and rejuvenation process of metallic glass by heating in an annealing furnace (comparative example); (d) is the relationship between the relaxation enthalpy of metallic glass and time when it is re-toughened (rejuvenated) by the method of the present invention and the existing method. Detailed Implementation

[0032] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0033] The memory effect is widespread in amorphous materials. It refers to the process by which the energy or volume of an amorphous material initially increases and then decreases during the second annealing step (after a two-step heat treatment process, first at a low temperature and then at a high temperature), eventually reaching equilibrium. Figure 1As shown in (b), this process of energy or volume increase is called the memory effect, which is also a process of rejuvenation of metallic glass after the first step of heat treatment aging. After this rejuvenation process, the energy state of the metallic glass, that is, the free volume content, will be restored to a certain extent. However, in the actual industrial application of metallic glass, annealing is an unavoidable measure to eliminate the residual stress caused by rapid cooling. This process leads to aging of the metallic glass (energy reduction, free volume reduction), which in turn leads to embrittlement of the metallic glass, seriously limiting its application. Based on this special background, we innovatively propose to use the memory effect to perform a second heat treatment on the aged sample to improve the energy state of the metallic glass, thereby improving the mechanical properties of the metallic glass (achieving the re-toughening of aged metallic glass). The specific scheme is as follows:

[0034] This invention provides a method for re-toughening metallic glass, comprising the following steps:

[0035] By subjecting cast metallic glass to an electric current treatment, a relaxed (aged) metallic glass is obtained.

[0036] The specific steps are as follows: Figure 1 As shown in (a), copper wires are wound around both ends of the cast metallic glass, a DC power supply is applied, and the current is maintained for a certain period of time before the power is cut off. The cast metallic glass is heated to the second set temperature of 0.8-0.85Tg. Differential scanning calorimetry analysis is performed on the obtained relaxed state (aged state) metallic glass to obtain the relaxation enthalpy ΔH2 of the relaxed state metallic glass. When the relaxation enthalpy ΔH2 of the cast metallic glass is less than ΔH1, it can be determined that the metallic glass has aged.

[0037] The relaxed metallic glass is then subjected to current treatment and then quenching to obtain re-toughened metallic glass (i.e., aged metallic glass).

[0038] The specific steps are as follows: Copper wire is wound around both ends of the relaxed-state metallic glass, and it is heated again under a higher current. After a period of time, the power is turned off, and the current is approximately 1.5-2 times that of the previous step, raising the temperature of the relaxed-state metallic glass to a first set temperature of 0.93-0.96Tg. Simultaneously, the sample is rapidly placed in liquid nitrogen (or ice water, or oil bath, or salt bath) for quenching, thus achieving the rejuvenation of the metallic glass. Differential scanning calorimetry (DSC) analysis is performed on the obtained relaxed-state (aged-state) metallic glass to obtain the relaxation enthalpy ΔH3. When ΔH3 > ΔH2, the aged-state metallic glass can be considered to have been rejuvenated; preferably, ΔH3 = 20%ΔH1 - 40%ΔH1. Here, Tg is the glass transition temperature of the metallic glass.

[0039] It should be noted that the present application passes current through the relaxation state (aging state) of the metal glass to heat it quickly to a higher temperature, at which point the memory effect can be activated, to some extent increasing the free volume content in the metal glass, improving the energy state of the metal glass, and then rapidly cooling by quenching to retain the increased free volume, achieving rejuvenation of the aged metal glass; wherein the heating method is different from the traditional external heat conduction (such as annealing furnace heating), but when the current passes through the internal resistance of the metal glass sample, heat (Joule heat) is generated, without the need for heat conduction from the surface to the interior, thus avoiding the temperature lag problem caused by heat conduction delay in traditional heating, greatly shortening the heating time; and Joule heat is generated synchronously in each region of the metal glass sample, so the temperature distribution is more uniform from the beginning, reducing the temperature difference caused by heat conduction, and even in large-size or complex-geometry samples, the size effect can be minimized.

[0040] Further, the present application passes current through the as-cast metal glass, under the action of resistance, the sample temperature rises, causing the free volume in the metal glass to annihilate, thereby reducing the energy state of the metal glass and causing the metal glass to age; the current treatment heats up quickly, further improving the re-toughening efficiency of the metal glass, and also releasing the residual stress in the metal glass.

[0041] In rejuvenating (rejuvenation) the aged state (relaxation state) metal glass, the current treatment heats it to 0.93-0.96Tg, which is below the glass transition temperature Tg of the metal glass, to ensure that the metal glass remains solid and does not deform, and the temperature is high enough to produce enough free volume to achieve a high degree of rejuvenation. When aging the as-cast metal glass by current treatment, it is heated to 0.8-0.85Tg, which can ensure aging in a short time and avoid high temperatures that enter the undercooled liquid state and destroy the slow relaxation environment required for aging.

[0042] The current size during the above current treatment is adjusted according to the size of the sample, when the diameter of the as-cast metal glass is 2-4mm and the length is 20-24mm; in the step of passing current through the as-cast metal glass: the current is 12-18A, and the time is 4.5-5.5h; in the step of passing current through the relaxation state of the metal glass: the current is 18-27A, and the time is 20-60s.

[0043] The as-cast metallic glass is a metallic glass rod produced by an arc melting and casting system, and specifically includes the following steps: selecting pure metal raw materials of certain quality, and ultrasonically cleaning the raw materials with alcohol for 2 minutes; selecting cylindrical pure copper molds of different sizes, and casting the raw materials after being uniformly melted in a crucible to obtain metallic glass rods of different sizes. When the casting mold is selected, the mold with a proper diameter is selected according to the quality of the raw materials, so that the alloy melt can fill the mold, and the metallic glass rod with good surface quality is obtained; and the obtained metallic glass rod is polished to remove burrs, and is ultrasonically cleaned with alcohol for current treatment.

[0044] In addition, the method for rejuvenating the metallic glass based on the current driving memory effect has the following advantages compared with the prior art:

[0045] (1) The process is simple, suitable for various conductive metallic glasses, suitable for samples of any shape and size, and non-destructive to the samples, and has high industrial application value.

[0046] (2) The process does not change the shape and amorphous structure of the metallic glass.

[0047] (3) The mechanical properties of the sample obtained by the rejuvenation method are greatly improved, and even better than the as-cast sample.

[0048] The application will be further described below in combination with specific examples and comparative examples.

[0049] In the examples and comparative examples, the as-cast metallic glass is prepared by the following method:

[0050] Elemental metals Zr, Cu, Ni and Al with a purity higher than 99.9% are mixed according to a certain atomic percentage (Zr64.13Cu15.75Ni10.12Al10), and then melted by an arc melting furnace under the protection of high-purity argon, and the melting is repeated for 8 times to obtain an alloy ingot; the metallic glass rod samples (as-cast metallic glass) with diameters of 2mm, 3mm and 4mm are obtained by copper mold suction casting or casting forming method.

[0051] Example 1

[0052] The embodiment provides a rejuvenation method of metallic glass, which includes the following steps:

[0053] Specifically, the copper wire is wound on both ends of the as-cast metallic glass with a diameter of 2mm and a length of 24mm, and a direct current power is turned on for 5h and then turned off to obtain a relaxed state (aged state) metallic glass; wherein the current is 12A;

[0054] Then copper wire is wound on both ends of the above relaxed state metal glass, and after power-on for 20s using a direct current power supply, power is turned off, and then the metal glass is cooled in liquid nitrogen to obtain the re-toughened metal glass (i.e. the rejuvenated metal glass); wherein the current size is 18A.

[0055] Example 2

[0056] The embodiment provides a re-toughening method of a metal glass, comprising the following steps:

[0057] The step is specifically: copper wire is wound on both ends of the as-cast metal glass with a diameter of 3mm and a length of 20mm, and after power-on for 5h using a direct current power supply, power is turned off to obtain the relaxed state (aged state) metal glass; wherein the current size is 18A;

[0058] Then copper wire is wound on both ends of the above relaxed state metal glass, and after power-on for 60s using a direct current power supply, power is turned off, and then the metal glass is cooled in liquid nitrogen to obtain the re-toughened metal glass (i.e. the rejuvenated metal glass); wherein the current size is 26A.

[0059] Example 3

[0060] The embodiment provides a re-toughening method of a metal glass, comprising the following steps:

[0061] The step is specifically: copper wire is wound on both ends of the as-cast metal glass with a diameter of 4mm and a length of 20mm, and after power-on for 5h using a direct current power supply, power is turned off to obtain the relaxed state (aged state) metal glass; wherein the current size is 18A;

[0062] Then copper wire is wound on both ends of the above relaxed state metal glass, and after power-on for 60s using a direct current power supply, power is turned off, and then the metal glass is cooled in liquid nitrogen to obtain the re-toughened metal glass (i.e. the rejuvenated metal glass); wherein the current size is 27A.

[0063] Comparative Example 1

[0064] The embodiment provides a re-toughening method of a metal glass, comprising the following steps:

[0065] The as-cast metal glass with a diameter of 2mm and a length of 4mm is annealed at 557K for 5h to obtain the relaxed state (aged state) metal glass;

[0066] The above relaxed state (aged state) metal glass is annealed at 642K for 90s, and then cooled in liquid nitrogen to obtain the re-toughened metal glass (i.e. the rejuvenated metal glass).

[0067] Comparative Example 2

[0068] The present comparative example provides a method for re-toughening of metallic glasses, comprising the following steps:

[0069] The as-cast metallic glass with a diameter of 2 mm and a length of 24 mm was annealed at 557 K for 5 h to obtain a relaxed (aged) metallic glass;

[0070] The relaxed (aged) metallic glass was annealed at 642 K for 180 s and then cooled in liquid nitrogen to obtain a re-toughened metallic glass (i.e. a rejuvenated metallic glass).

[0071] Comparative Example 3

[0072] The present comparative example provides a method for re-toughening of metallic glasses, comprising the following steps:

[0073] The as-cast metallic glass with a diameter of 4 mm and a length of 20 mm was annealed at 557 K for 5 h to obtain a relaxed (aged) metallic glass;

[0074] The relaxed (aged) metallic glass was annealed at 642 K for 420 s and then cooled in liquid nitrogen to obtain a re-toughened metallic glass (i.e. a rejuvenated metallic glass).

[0075] The corresponding parameters of the above examples and comparative examples are shown in Table 1.

[0076] Table 1

[0077]

[0078] The performance energy, mechanical properties characterization and the like of the metallic glasses obtained in the above examples and comparative examples were characterized, and the results are shown in Figures 2 to 6 .

[0079] wherein, Figure 2 DSC curves and energy statistics of metallic glasses in different states. From Figure 2 As can be seen from (a)-(c), the as-cast sample shows a clear exothermic peak before experiencing glass transition, indicating that it is in a high-energy state. After the first step of current annealing (12-18 A, 5 h), the exothermic peak disappears and is accompanied by the appearance of an endothermic peak, indicating that the sample has aged after the first step of current treatment. The aged sample obtained above is subjected to a second treatment with a higher current (18-27 A, 20-60 s), and the endothermic peak of the amorphous sample disappears and the exothermic peak reappears, indicating that the sample is in a high-energy state at this time, i.e. the second current heat treatment realizes the rejuvenation of the aged metallic glass. Figure 2(d) The energy states of the as-cast, aged and rejuvenated metallic glass samples are shown in detail. It can be clearly found that the second current heat treatment can increase the energy of the amorphous alloy, and with the increase of the second current heat treatment time, the energy state of the amorphous alloy first increases and then tends to be stable. This phenomenon of energy first increasing in the second current heat treatment process is a manifestation of the memory effect of metallic glass.

[0080] Figure 3 The XRD patterns of the metallic glass in different states can be found that all samples exhibit typical dumpling peaks of amorphous alloy, and no crystal diffraction peak is found. At the same time, the transmission electron microscope photos exhibit typical diffraction rings and disordered structure of amorphous alloy, indicating that the metallic glass after current heat treatment still maintains a completely amorphous structure.

[0081] Figure 4 The hardness and compression performance results of the metallic glass in different states. Figure 4 (a) shows that the hardness of the amorphous alloy increases after aging, while the hardness decreases after rejuvenation. It can be found that the hardness of the metallic glass after current memory effect rejuvenation will soften. Figure 4 (b) and (c) are the compression stress-strain curves and plastic strain statistics of the metallic glass in different states, respectively. It can be found that aging significantly reduces the plasticity of the metallic glass, making the amorphous alloy brittle. On the contrary, rejuvenation can significantly improve the plasticity of the metallic glass. Under the best condition, the plasticity of the rejuvenated sample is even significantly better than that of the as-cast sample. It shows that the memory effect driven by current not only can significantly improve the plasticity of the metallic glass, but also can be used to improve the mechanical properties of the aged metallic glass.

[0082] Figure 5 The nanoindentation creep results of the metallic glass in different states. It can be seen that the creep performance of the as-cast amorphous alloy is the worst, and the creep performance is improved after aging. The rejuvenated sample shows the best anti-creep performance.

[0083] Figure 6 The DSC curves of the metallic glass in different states when the memory effect is activated and rejuvenated by annealing furnace heating, and the change relationship of relaxation enthalpy with time when rejuvenated by two kinds of heating methods. From the DSC curves in (a)-(c), it can be seen that when the two-step annealing treatment is carried out by annealing furnace heating, the evolution trend of the DSC curve is consistent with that of the two-step current heating in Figure 2 , indicating that annealing furnace heating can also activate the memory effect to rejuvenate the aged metallic glass. However, it can also be seen that the DSC curve of the metallic glass after annealing furnace heating rejuvenation and the DSC curve of the as-cast metallic glass sample in the glass transition region (Tg) are different, which indicates that the memory effect of the metallic glass is not activated by annealing furnace heating. Figure 6(a) the dashed line box in (a) does not coincide, indicating that although the annealing furnace heating mode causes the metallic glass to continue to age to some extent, and as the sample size increases, the trend of non-coincidence continues to increase, and there is also an "overshoot" endothermic peak, which indicates that the use of annealing furnace heating mode to activate the memory effect to rejuvenate the metallic glass (low temperature part, corresponding to the beta relaxation) inevitably brings a certain degree of aging (high temperature aging behavior in the glass transition region, corresponding to the alpha relaxation part), making the rejuvenation effect worse. In addition, as can be seen from (d), the current heating rejuvenation requires a relatively short time and a relatively large degree of rejuvenation.

[0084] In the above performance test, the compression sample was prepared by the following method: the rod-shaped sample prepared in step 1-2 was cut into a cylindrical sample with a height-diameter ratio of 2:1 using a diamond cutter, the upper and lower end faces were polished parallel using a special clamp and #1000-#5000 sandpaper, and then polished to a mirror surface. The nanoindentation creep sample was prepared by the following method: the rod-shaped sample of different states (as-cast, aged, and rejuvenated) was embedded in transparent cold mounting material, then ground on different types (#4000-#5000) of sandpaper using a self-made grinder, and finally polished with a 50 nm particle size SiO2 suspension to achieve a mirror surface effect on the test surface.

[0085] Those skilled in the art will readily understand that the advantageous technical features of the above-mentioned modes can be freely combined and superimposed without conflict.

[0086] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for re-toughening metallic glass, characterized in that, Includes the following steps: A DC power supply is used to pass current through the cast metallic glass to release the residual stress within the cast metallic glass, and the cast metallic glass is heated to 0.8-0.85Tg to obtain a relaxed metallic glass; wherein the current is 12-18A; the current treatment time is 4.5-5.5h; Wherein, the relaxation enthalpy of the cast metallic glass is ΔH1; the relaxation enthalpy of the relaxed metallic glass is ΔH2; ΔH1>ΔH2; the diameter of the cast metallic glass is 2-4mm and the length is 20-24mm; The relaxed metallic glass is subjected to current treatment to raise its temperature to a first set temperature, and then quenched. Wherein, the first set temperature is lower than the glass transition temperature Tg of the metallic glass; the relaxation enthalpy of the quenched metallic glass is ΔH3; wherein, ΔH3 > ΔH2.

2. The method for re-toughening metallic glass according to claim 1, characterized in that, The first set temperature is 0.93-0.96 Tg.

3. The method for re-toughening metallic glass according to claim 1, characterized in that, In the step of passing an electric current through the relaxed metallic glass, the current is 18-27A and the time is 20-60s.

4. The method for re-toughening metallic glass according to claim 1, characterized in that, Before the step of performing current-passing treatment on the cast metallic glass, the method further includes: performing differential scanning calorimetry on the cast metallic glass to obtain the relaxation enthalpy ΔH1 of the cast metallic glass.

5. The method for re-toughening metallic glass according to claim 4, characterized in that, After the step of applying current to the cast metallic glass, the method further includes: performing differential scanning calorimetry on the relaxed metallic glass to obtain the relaxation enthalpy ΔH2 of the relaxed metallic glass.

6. The method for re-toughening metallic glass according to claim 4, characterized in that, After the quenching process, the method further includes: performing differential scanning calorimetry on the quenched metal glass to obtain the relaxation enthalpy ΔH3 of the quenched metal glass.

7. The method for re-toughening metallic glass according to claim 6, characterized in that, ΔH3 = 20%ΔH1 - 40%ΔH1.

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