CN113382815B

CN113382815B - Stable ingots for producing components made of bulk metallic glass

Info

Publication number: CN113382815B
Application number: CN202080011844.XA
Authority: CN
Inventors: T·格拉瑟; H·沙库尔沙哈比; E·迈尔克; H-J·瓦赫特
Original assignee: Holly Amroy Technology Co ltd
Current assignee: Holly Amroy Technology Co ltd
Priority date: 2019-02-13
Filing date: 2020-01-30
Publication date: 2023-05-12
Anticipated expiration: 2040-01-30
Also published as: TW202035718A; US20220118511A1; TWI791947B; CN113382815A; EP3695920A1; WO2020164916A1; EP3695920B1

Abstract

A method of producing an ingot made of a bulk glass forming alloy, comprising the steps of: providing a homogeneous melt of bulk glass forming alloy; casting the homogeneous melt into a mold, wherein the mold does not cool to below the glass transition temperature of the alloy for at least a second at a contact surface with the melt; and cooling the melt to below the glass transition temperature of the bulk glass forming alloy to obtain an ingot.

Description

Stable ingots for producing components made of bulk metallic glass

The present invention relates to a method of producing mechanically and thermally stable ingots (also known as preforms) made of alloys that form bulk metallic glass. The invention also relates to ingots of bulk glass forming alloys (bulk glass-forming alloys) made by the method according to the invention, and to the use of such ingots in casting processes.

The metallic glass found in California Institute of Technology about 50 years ago has been the subject of much research since. The processability and properties of such materials have been able to be improved continuously over the years. Although the original metallic glass was a simple binary alloy (composed of two components), its production required about 10 ⁶ Kelvin/second (K/s) coldBut at a cooling rate, but more recently and more complex alloys can be converted to glassy state at significantly lower cooling rates of a few K/s. This has a significant effect on process control and achievable components. The cooling rate at which the melt solidifies from this point on, without recrystallization, in the form of glass is called the critical cooling rate. Which is a system-specific parameter that depends greatly on the composition of the melt and additionally determines the maximum component thickness that can be achieved. Given that the thermal energy stored in the melt needs to be dissipated by the system at a sufficiently fast rate, it is apparent that only low thickness components can be made using a system with a high critical cooling rate. Thus, metallic glass was initially produced according to the melt spinning method (German: schmelzspinnfafahren). In this method, the melt is stripped onto a rotating copper wheel and solidified in a glass-like manner in the form of thin strips and/or sheets with thickness values in the range of a few percent to a few tenths of a millimeter. Other production methods are increasingly being used as new more complex alloys with significantly lower critical cooling rates are developed. Today's glass-forming metal alloys can be converted to the glassy state by simply pouring the melt into a cooled copper mold. The component thickness achievable in this case is alloy-specific, in the range from a few millimeters to a few centimeters. This type of alloy is known as Bulk Metallic Glass (BMG). Within the scope of the present invention, bulk metallic glass is understood to be a material having a critical casting thickness of at least 1 mm. A large number of such alloy systems are known today. They are generally classified according to their composition, with the alloying element having the highest weight fraction being referred to as the base element. Existing systems comprise, inter alia, noble metal-based alloys, such as gold-, platinum-and palladium-based bulk metallic glasses, pre-transition metal-based alloys, such as titanium or zirconium-based bulk metallic glasses, post-transition metal-based systems, such as copper, nickel or iron-based systems, and rare earth metal-based systems, such as neodymium or terbium.

In contrast to classical crystalline metals, bulk metallic glasses generally comprise at least one of the following properties:

higher specific strength, which allows for example thinner wall thickness;

higher hardness, which makes the surface particularly resistant to scratches;

-much higher elasticity (elastic elasticity) and resilience (resiliency);

-thermoplastic deformability; and

higher corrosion resistance.

Components made of bulk metallic glass can be produced by casting methods, because the cooling rates required for amorphous solidification can be achieved in the methods. In order to obtain amorphous components from bulk metallic glass, it is often necessary to rapidly transfer a melt of the bulk glass forming alloy into a mold. Preferably, this is achieved by filling the melt into the casting mould by means of injection (injection moulding) or suction (vacuum casting). By this means a high cooling rate can be achieved and three-dimensional components can be made from bulk metallic glass. The use of casting methods, such as injection molding, enables low manufacturing tolerances.

Casting methods require processing of alloy ingots that act as reservoirs of material to be processed and can be uniformly melted. For this reason, the ingot must have sufficient volume to provide enough material for the entire casting and also to fill the extra space (e.g., gate) of the mold. It is therefore desirable to provide ingots of the largest size possible.

To produce an ingot from a bulk glass forming alloy, a homogeneous bulk glass forming alloy is first produced. To this end, the individual components are mixed together and heated above the melting point to produce a homogeneous alloy. The individual components can be melted, for example, in an electric arc or by means of induction heating. The homogeneous alloy is then filled into a mold and chilled to form an ingot. Generally, these ingots are in the shape of cylindrical bars. In order for the ingot to contain enough material to completely fill the mold for the casting process of the three-dimensional component, the ingot must be large enough in size. Typical diameters of cylindrical ingots made of bulk glass forming alloys are in the range of about 20 mm. The length of the ingot is preferably at least 3cm.

A method is known from US5279349, wherein amorphous molded parts can be obtained by using a preheated mold. Here, the melt is exposed to pressure during cooling. With the method, a very small non-ingot can be made because the molded part must not exceed the critical casting thickness in any dimension. However, due to their limited size, the fully non-ingot can only provide a very limited amount of material for the casting process. Another disadvantage of non-ingots in the use of casting methods is that they can only slowly melt due to their poor thermal conductivity.

The production of high quality ingots made of materials having high critical casting thicknesses and having dimensions exceeding the critical casting thickness is difficult. First, there is a significant amount of scrap in the production process, as it is known that ingots often crack as early as in the production process. In addition, some ingots made by conventional techniques are cracked during transportation or during heating during the actual steps of producing three-dimensional components by casting methods. Ingot cracking during the production of three-dimensional components is disadvantageous because the cracks formed interrupt heat conduction. This increases the process duration of the production of the three-dimensional component. In order to prevent cracking of conventional ingots, which are not detrimental to the production process, it is necessary to heat the ingot very slowly to the melting temperature. Typically, melting of the ingot takes at least 80 seconds.

Object of the Invention

It is an object of the present invention to provide ingots made of bulk glass forming alloys having high critical casting thickness which do not crack during production and which can be heated more rapidly during hot working, such as injection molding.

Furthermore, it is an object of the present invention to provide a method for producing ingots made of bulk glass forming alloys having a high critical casting thickness which do not crack during the production process.

It is another object of the present invention to provide ingots made of bulk glass forming alloys which can heat faster than conventional ingots.

The subject matter of the independent claims contributes to solving at least one of the above-mentioned objects.

A first aspect of the invention relates to a method of producing an ingot (20) of bulk glass forming alloy, comprising the steps of:

a. providing a homogeneous melt (10) of bulk glass forming alloy;

b. casting the homogeneous melt into a mold, wherein the mold does not cool to below the glass transition temperature of the alloy for at least 5 seconds at the contact surface with the melt; and

c. the ingot (20) is obtained while cooling the melt below the glass transition temperature of the bulk glass forming alloy.

The composition of the bulk glass forming alloy is not limited in any way. Preferably, bulk glass forming alloys are understood to be alloys having a critical casting thickness of at least 1 mm. This means that the alloy can be amorphous solidified to a thickness of 1mm at a suitable cooling rate.

Bulk glass forming alloys are understood to be alloys that under certain thermal conditions can contain metal binding properties in the solid state and at the same time can contain an amorphous phase, i.e. an amorphous phase. The alloy may be based on different elements. Herein, "based on" is understood to mean that the respective element represents the largest fraction relative to the weight of the alloy. The components which are preferably also possible as a basis for the alloy may be selected, for example, from the group consisting of:

A. metals of groups IA and IIA of the periodic table of elements, such as magnesium, calcium;

B. metals of groups IIIA and IVA, for example aluminium or gallium;

C. front transition metals from groups IVB to VIIIB, such as titanium, zirconium, hafnium, niobium, tantalum, chromium, molybdenum, manganese;

D. post-transition metals from group VIIIB, IB, IIB, such as iron, cobalt, nickel, copper, palladium, platinum, gold, silver, zinc;

E. rare earth metals, e.g. scandium, yttrium, terbium, lanthanum, cerium, neodymium, gadolinium, and

F. nonmetallic materials, such as boron, carbon, phosphorus, silicon, germanium, sulfur

Preferred combinations of elements in bulk metallic glass are selected from:

late transition metals and non-metals, wherein the late transition metals are the basis, such as Ni-P, pd-Si, au-Si-Ge, pd-Ni-Cu-P, fe-Cr-Mo-P-C-B;

front transition metal and rear transition metal, either of which may Be the basis, for example Zr-Cu, zr-Ni, ti-Ni Zr-Cu-Ni-Al, zr-Ti-Cu-Ni-Be;

metals from group B and rare earth metals, wherein metal B is the basis, such as Al-La, al-Ce, al-La-Ni-Co, la- (Al/Ga) -Cu-Ni; and

metals from group A and late transition metals, where metal A is the base, e.g. Mg-Cu, ca-Mg-Zn, ca-Mg-Cu

In addition, particularly preferred examples of alloys from which bulk metallic glass can be formed are selected from the group consisting of Ni-Nb-Sn, co-Fe-Ta-B, ca-Mg-Ag-Cu, co-Fe-B-Si-Nb, fe-Ga- (Cr, mo) (P, C, B), ti-Ni-Cu-Sn, fe-Co-Ln-B, co- (Al, ga) - (P, B, si), fe-B-Si-Nb, and Ni- (Nb, ta) -Zr-Ti. In particular, the bulk metallic glass may be a Zr-Cu-Al-Nb alloy. Preferably, the Zr-Cu-Al-Nb contains 23.5 to 24.5 wt.% copper, 3.5 to 4.0 wt.% aluminum and 1.5 to 2.0 wt.% niobium in addition to zirconium, wherein the parts by weight add up to 100 wt.%. The latter alloy can

Is named from Heraeus Deutschland GmbH. In a further particularly preferred embodiment, the bulk glass forming alloy may contain or consist of the elements zirconium, titanium, copper, nickel and aluminum. Particularly stable ingots can be made from bulk glass forming alloys having the composition described. Alloys particularly suitable for producing stable ingots comprise the composition Zr _52.5 Ti ₅ Cu _17.9 Ni _14.6 Al ₁₀ Wherein the index specifies the mol-% of the respective element in the alloy.

Because of the inherent thermal conductivity of the material, there is a maximum casting thickness even at the maximum cooling rate achievable, so the casting needs to be smaller in at least one dimension than it is still able to form a homogeneous amorphous phase. Preferably, the bulk glass forming alloy comprises a critical casting thickness of at least 5mm, in particular at least 7mm, particularly preferably at least 10mm. Within the scope of the present invention, critical casting thickness (maximum casting thickness) is a measure of how easily or how difficult it is to transform a metal alloy into a glassy state.

To determine critical casting thickness within the scope of the present invention, the test alloy is processed in an arc to form a uniform melt and then poured into a water cooled copper mold (also known as a die). The mass of the copper mold is preferably at least 7 times greater than the mass of the melt of the test alloy filled therein. The temperature of the homogeneous melt prior to casting is preferably at least 200 ℃, in particular 300 ℃, particularly preferably at least 400 ℃ above the melting temperature. The temperature of the copper mold was 20 ℃. To determine the critical casting thickness, cylindrical molded parts are cast having incremental diameters (e.g., 2mm, 3mm, 4mm, 5mm, 6mm, etc.) that differ by 1 mm. The resulting cylindrical molded parts were tested for crystallization fraction by dynamic Differential Scanning Calorimetry (DSC). The reported critical casting thickness is a cylinder diameter 1mm smaller than the cylinder diameter at which the crystalline phase was first measured by DSC. The presence of the crystalline phase was measured by DSC procedure 2) as described herein.

In step a) of the present invention, a homogeneous melt of bulk glass forming alloy is provided. It is preferred to provide a homogeneous melt by melting and combining the individual elements of the alloy. The melting of the individual elements is preferably carried out in an electric arc or by means of induction heating. The temperature of the homogeneous melt is preferably at least 200 ℃, in particular at least 300 ℃, particularly preferably at least 400 ℃, above the melting temperature of the respective bulk glass forming alloy. In a preferred embodiment, the temperature of the melt, measured in degrees celsius, is at least 20%, in particular at least 50%, above the melting temperature of the alloy, as this enables particularly stable ingots to be made.

In step b), the homogeneous melt is cast into a casting mold. The shape of the mould is not limited in any way according to the invention. Preferably, the casting mould is cylindrical. Preferably, the volume of the mold to be filled is greater than the critical casting thickness of the bulk glass forming alloy in all three dimensions of the space. The material of the casting mould may preferably be selected from steel, titanium, copper, ceramic or graphite. Preferably, the mould comprises means for actively heating and/or cooling the mould. In one embodiment of the invention, the mold may be actively heated, such as by electrical heating.

The ratio of the mold weight to the melt weight is preferably in the range of 7:1 or more, particularly preferably in the range of 10:1 or more. In a preferred embodiment of the invention, the mold may be in the region of contact with the meltAnd (3) coating. The material of the coating of the casting mould is preferably selected from boron nitride, alumina (e.g. Al ₂ O ₃ ) And yttrium oxide (e.g. Y ₂ O ₃ ). Preferably, the coating comprises or consists of a powder. The thickness of the coating, in particular of the powder coating, may in one embodiment be in the range of 10-50 μm. The powder layer may have a beneficial effect on the mechanical properties of the ingot to be produced. The coating in particular aids in easier removal of the ingot from the mold.

According to the invention, the casting mould is not cooled at the contact surface with the melt to a temperature below the glass transition temperature of the bulk glass forming alloy for at least 5 seconds, in particular for at least 10 seconds, particularly preferably for at least 30 seconds. Within the scope of the present invention, the term "melt" is used even after the liquid melt has been transferred into the mold, even if the solidification process has started and the bulk glass forming alloy has partially or completely solidified, as long as the temperature has not been reduced below the glass transition temperature.

In a preferred embodiment of the invention, none of the contact surfaces of the mold with the melt is cooled below the glass transition temperature of the bulk glass forming alloy for a specified period of time. Determination of the glass transition temperature of the alloy is described in the "methods". In a preferred embodiment of the invention, the temperature of the casting mould at the contact surface with the melt is at least 10 ℃, in particular at least 20 ℃, particularly preferably at least 40 ℃ or at least 80 ℃ above the glass transition temperature of the bulk glass forming alloy within the time specified above.

To measure the mold temperature at the contact surface, a temperature measurement probe may be suitably incorporated into the mold so as to extend to the contact surface of the mold with the melt and to take measurements at this location. The temperature measurement is preferably made at a position equal to half the length of the longest dimension of the ingot. Preferably, the mold temperature before filling with the melt is set so that after casting, the mold temperature at the location of contact with the melt does not drop below the glass transition temperature of the alloy for at least 5 seconds, in particular at least 10 seconds, particularly preferably at least 30 seconds, after contact with the mold.

Preferably, the mold is heated prior to contact with the melt. The temperature of the casting mould is preferably set to at least 250 ℃, in particular at least 400 ℃, particularly preferably at least 500 ℃, just prior to casting the melt. The casting mould may be heated, for example in a furnace. Alternatively, the mold may be actively heated, such as by electrical heating.

Preferably, no additional pressure significantly above the normal atmospheric pressure is applied to the melt after casting the melt. "significantly higher than normal atmospheric pressure" is understood within the scope of the present invention to mean an overpressure of 1 bar or more.

In step c), the ingot (20) is obtained while cooling the melt below the glass transition temperature of the bulk glass forming alloy. Preferably, the melt is cooled to room temperature. The cooling rate in step c) is not limited in any way according to the invention. In a possible embodiment, the melt is allowed to cool to room temperature without any additional intervention (heating and/or cooling). Alternatively, the melt may be actively cooled below the glass transition temperature to accelerate the process.

The method according to the invention enables the formation of ingots from bulk glass forming alloys that do not crack during the production process. In addition, the method enables the production of ingots that do not crack when heated to the melting temperature of the alloy for a period of up to 50 seconds. In particular, ingots can be made that do not crack when dropped three times from a height of 30 cm onto a flat horizontal steel surface. In particular, the method enables the production of ingots that do not contain an amorphous layer at the surface. The absence of an amorphous layer can be determined in an optical microscope.

Ingot casting

Another aspect of the invention relates to an ingot of a bulk glass forming alloy, wherein the alloy has a critical casting thickness of at least 5mm and wherein the ingot has an elongation in all three dimensions of space that is greater than the critical casting thickness, characterized in that the ingot comprises a crystallization fraction of at least 90 wt%, particularly at least 95 wt%, particularly preferably at least 98 wt%, as measured by DSC.

Preferably, the critical casting thickness of the alloy is at least 7mm, in particular at least 10mm. The ingots according to the present invention may be made by the methods described herein. In a preferred embodiment, the ingot according to the invention does not comprise an amorphous layer on the surface. Within the scope of the present invention, the term "not comprising an amorphous layer" is understood to mean a layer which is not thicker than 200 μm, in particular not thicker than 100 μm, particularly preferably not thicker than 50 μm. The absence of an amorphous layer may preferably result in a reduction of internal stresses in the ingot. The absence of an amorphous layer on the surface of the ingot can be determined by means of optical microscopy (reflected light microscopy). For this purpose, a cross section of the ingot is produced by means of a diamond saw. This cross section is also known as a metallographic micrograph or cross section. The absence of amorphous components can be determined by the absence of macroscopic phase transitions in the optical microscope. The phase transitions can be identified as transitions of different colors or different contrasts in the optical microscope. Reference should be made in this respect to fig. 1 to 3. Fig. 1 shows a photomicrograph of a cross-section of an ingot containing amorphous regions. The amorphous region can be detected as a bright region (arrow 1) near the edge. The interior region of the test ingot did not contain a bright area (arrow 2). In contrast, fig. 2 shows a micrograph of a cross section of an ingot without amorphous regions. This is confirmed by the uniform appearance of the material without any bright spots. Fig. 3 shows a metallographic micrograph of the sample from fig. 2 at a higher magnification. The polycrystalline structure and/or their grain boundaries are clearly visible therein. It is also evident that the crystalline structure of the ingot according to the invention extends all the way to the edge, which confirms the absence of an amorphous phase (for example in the circled area). If an amorphous phase is present, it is preferably formed first at the edges, since the cooling rate is probably highest at this location.

In one embodiment, the total volume of the amorphous layer on the ingot may be 5% or less, particularly 3% or less. Crystallinity of the ingots can be measured by Differential Scanning Calorimetry (DSC). Preferably, the ingot is solid and does not contain hollow spaces, such as air inclusions. The shape of the ingot is not limited in any way according to the invention. The ingot may comprise a cylindrical shape in one embodiment. Preferably, the diameter of the cylinder has a value of at least 5mm, in particular at least 15mm, particularly preferably at least 25mm, provided that the diameter is greater than the critical casting thickness of the bulk glass forming alloy. The length of the cylinder is preferably at least 3cm.

Another aspect of the invention relates to a method of producing a three-dimensional component from bulk metallic glass by casting, in particular injection molding, by using the bulk glass of the invention to form an ingot of an alloy.

In the production of three-dimensional components by means of casting processes, such as injection molding, the cast ingot according to the invention is melted to produce a homogeneous melt (30). Preferably, the complete melting of the cast ingot (20) takes no longer than 60 seconds, in particular no longer than 40 seconds, particularly preferably no longer than 20 seconds, whereby the cast ingot can be heated without cracking.

In general, conventional ingots can only melt significantly slower, otherwise they can crack. This is associated with the above-mentioned drawbacks. Typically, the heating time for a known ingot of the same size is around 80 seconds. After melting the ingot (20), the homogeneous melt (30) is cast, in particular injected, into a casting mold for a three-dimensional component (40). Preferably, the mould used to produce the three-dimensional component by means of the casting method is suitably dimensioned so that it does not exceed the critical casting thickness of the alloy used in the method at any location, as this enables a completely amorphous three-dimensional component to be produced. In particular, the ingot may be used to produce three-dimensional components that may be produced at high throughput in an injection molding machine.

Measurement method

X-ray diffraction method (XRD)

XRD measurements were carried out in accordance with DIN EN 13925-1:2003-07 and DIN EN 13925-2:2003-07. Cross sections of the test material were made using a diamond saw. The plane surface of the cross section is about 1cm ² Within a range of (2). The measurement details generally used herein can be summarized as follows: diffraction Bragg-Brentano; a detector, a scintillation counter; radiation Cu _Kα

The source is 40kV and 25mA; the measuring method is reflection.

The empty sample holder is first measured as an internal reference to determine the background signal. The background measurement is subtracted from all subsequent measurements of the test sample.

The discrete diffraction signals in the diffraction pattern, if any, can be analyzed according to the debye-scherrer method using the bragg equation. If there are any discrete crystallization peaks visible above the statistical noise, the estimated crystallization fraction is at least 5% by weight. If the diffraction pattern does not show signs of sharp diffraction signals, the crystallization fraction is less than 5%.

DSC measurement

DSC measurements within the scope of the present invention are performed according to DIN EN ISO 11357-1:2017-02 and DIN EN ISO 11357-3:2018-07. Samples to be measured in the form of thin discs or sheets (about 80-100 mg) are placed in a measuring device (NETZSCH DSC 404F1,NETZSCH GmbH,Germany). The heating rate was 20.0K/min. Using Al ₂ O ₃ As crucible material. The heat flow is measured relative to an empty reference crucible, so that only the thermal behaviour of the sample is measured.

The measurement procedure was performed according to the following steps:

a) The sample to be measured is heated to a temperature just below the melting temperature (t=0.75×tm) at the heating rate specified above and the heat flow is measured. Once the heat flow associated with the phase transition can no longer be measured, the measurement is completed. In particular, the measurement is stopped once the exothermic signal associated with the crystallization process is completely detected. In examples included herein, the measurement is performed, for example, from room temperature to about 600 ℃.

b) The sample was allowed to cool to room temperature.

c) The sample was reheated to the same temperature as in step a) at the same heating rate and the heat flux was measured.

d) Subtracting the measurement from step c) from the measurement from step a) to obtain a difference between the measurements. By forming an integral, the difference between the measurements is used to determine the enthalpy of crystallization (if any).

1) Measurement on a sample with a small amorphous fraction (e.g. an ingot according to the invention)

Samples that are predominantly crystalline and contain only a small proportion of amorphous phase are expected to be measured according to the measurement methods specified above. In step a) a sample, for example from an ingot according to the invention, is heated to a temperature of t=0.75×tm (75% of the melting temperature (Tm) in degrees celsius). If the heat flow cannot be measured near the crystallization temperature after subtracting the reference measurement from step c), the sample is assumed to be completely crystalline (measurement inaccuracy 5%). After passing this measurement method, the complete crystallinity of the sample can be additionally confirmed by XRD by the absence of a broad non-specific signal in the diffractogram indicative of the amorphous phase. The amorphous fraction of the sample greater than 5 wt% can be determined by comparing the enthalpy of crystallization of the unknown sample with the value of a completely amorphous sample from DSC procedure 2) (see below).

2) Determination of critical casting thickness

Samples of each cast cylinder were measured by DSC to determine critical casting thickness. As long as the diameter of the cylinder is below the critical casting thickness, the sample is completely amorphous before the start of the measurement and crystallises during the DSC measurement in step a) of the measurement method. The enthalpy of crystallization of the alloy is determined from measurements of the fully amorphous material. Enthalpy of crystallization was determined for all samples with increasing cylinder diameter. The enthalpy of crystallization determined for samples with cylinder diameters below the critical casting thickness is constant within the limits of measurement inaccuracy. Once the cylinder diameter exceeds the critical casting thickness, a smaller enthalpy of crystallization is measured in the DSC measurement than at smaller diameters, as a portion of the material has crystallized and this no longer occurs during the DSC measurement. The critical casting thickness is determined as the cylinder diameter to which the enthalpy of crystallization is constant at increasing diameters.

3) Glass transition temperature

Within the scope of the present invention, the glass transition temperature is measured according to ASTM E1365-03 as follows. The test sample was placed in a crucible in a DSC apparatus (NETZSCH DSC 404F1,NETZSCH GmbH,Germany). The system was heated and cooled according to the following protocol and the respective heat flows were measured in steps a) and c).

a) Heating to a temperature of 0.75 Tm at a heating rate of 20K/min

b) Cooling to room temperature

c) Heating to the same temperature as in step a) at the same heating rate; and

d) Cooled to room temperature.

The result obtained in this experiment is the enthalpy vs temperature of the sample. Crystallization of the amorphous sample occurs in step a). The thermal behaviour of the completely crystallized sample is recorded in step c).

To determine the glass transition temperature, the measurement from step c) is subtracted from the measurement from step a). The resulting curve contains the endothermic transition at a lower temperature and the exothermic signal at a higher temperature. The signal at the higher temperature corresponds to the crystallization process. The endothermic signal corresponds to a glass transition. To determine the glass transition temperature, the tangent to the baseline is determined (by linear fitting) prior to the glass transition range. The second tangent is measured at the inflection point of the glass transition range (peak corresponding to the first derivative). The temperature value at the intersection of these two tangents is indicative of the glass transition temperature (T according to AST;1356-03 _f )。

Examples

The individual components are melted in an inert gas by means of induction melting to form a composition Zr _52.5 Ti ₅ Cu _17.9 Ni _14.6 Al ₁₀ Is a homogeneous alloy of (a). The alloy has a glass transition temperature of 403 ℃. A total of 80 grams of the homogeneous alloy was heated in a melting crucible by induction heating to a temperature above the melting temperature (805 ℃) of the alloy. The temperature of the respective melt in each experiment is shown in table 1. The casting mold was heated in a furnace to the temperatures specified in table 1 for each case. Subsequently, the respective homogeneous melts according to table 1 were filled into a casting mold. The mould is cylindrical and has an inner diameter of 19 mm. The temperature of the melt is measured continuously after filling it into a cylindrical mold. The measured values of the melt temperature after 10 seconds in the casting mold in each case are given in table 1.

Examples	1	2	3	4	5
						T _{Melt body} [℃]	1050	1100	1200	1250	1350
T _{Casting mould} [℃]	50	50	250	400	600
						Casting mould	Copper (Cu)	Steel and method for producing same	Steel and method for producing same	Steel and method for producing same	Steel and method for producing same
Weight ratio of	1:17	1:15	1:9	1:15	1:15
						Coating of casting mould	Without any means for	BN	Y ₂ O ₃	BN	Al ₂ O ₃

T after 10s _{Casting mould} [℃]

150

410

420

About 550

Ingot quality

Difference of difference

Good quality

Excellent in

TABLE 1

Examples 1 and 2 in table 1 are reference examples and examples 3 to 5 are examples according to the invention. The quality of the ingots was evaluated according to the following criteria: the poor quality castings have cracked while cooling in the mold. Good quality ingots remained intact when heated to a melting temperature of at most 50 seconds at a power of 5 kW. The excellent quality ingots were additionally resistant to three trials from a height of 30 cm falling onto flat steel plates without cracking. It is apparent from examples 1-5 that ingots having a melt temperature above the glass transition temperature after 10 seconds are significantly more stable than ingots having a melt temperature below the glass transition temperature.

Description of the drawings:

fig. 1 shows an optical microscope image showing a cross section of an ingot made according to example 1 as a reference experiment. The bright areas in this cross section, indicated by the arrows in an exemplary manner, show amorphous areas (arrow 1) surrounded by deeper crystalline areas (arrow 2). Further, as is apparent from fig. 1, the ingot is cracked.

Fig. 2 shows an optical microscope image showing a cross section of an ingot made according to example 4. The cross section of the ingot according to example 4 shows a uniform distribution of material, without showing bright areas of amorphous phase.

Fig. 3 shows an enlarged view of the sample according to the invention from fig. 2. The image shows the polycrystalline structure of the ingot extending up to the edge region of the cross section.

Fig. 4 shows a schematic of the process flow from the individual components (5) of the bulk glass forming alloy to the component (40) made of bulk metallic glass. The process flow comprises the following steps: individual components of bulk glass forming alloy (5), homogeneous melt (10), ingot made of bulk glass forming alloy (20), homogeneous melt of bulk glass forming alloy (30), and assembly made of bulk metallic glass (40).

Claims

1. A method of producing an ingot of bulk glass forming alloy comprising the steps of:

a. providing a homogeneous melt of bulk glass forming alloy;

c. cooling the melt to below the glass transition temperature of the bulk glass forming alloy while obtaining an ingot,

wherein no additional pressure is applied to the melt after casting the melt that is significantly above the normal atmospheric pressure, which means an overpressure of 1 bar or more.

2. The method of claim 1, wherein the mold is not cooled to below the glass transition temperature of the alloy for at least 10 seconds at the contact surface with the melt.

3. The method of claim 1, wherein the bulk glass forming alloy has a critical casting thickness of 5mm or greater, wherein critical casting thickness is determined by dynamic differential scanning calorimetry as follows: processing the test alloy in an electric arc to form a homogeneous melt and then pouring into a water cooled copper mold, wherein the mass of the copper mold is at least 7 times greater than the mass of the melt of the test alloy filled therein, wherein the temperature of the homogeneous melt is at least 200 ℃ above the melting temperature prior to casting, wherein the temperature of the copper mold is 20 ℃, and wherein the crystalline fraction of a cylindrical molded part having an incremental diameter differing by 1mm and the cylindrical molded part thus produced is tested by means of dynamic differential scanning calorimetry.

4. The method of claim 2, wherein the bulk glass forming alloy has a critical casting thickness of 5mm or greater, wherein critical casting thickness is determined by dynamic differential scanning calorimetry as follows: processing the test alloy in an electric arc to form a homogeneous melt and then pouring into a water cooled copper mold, wherein the mass of the copper mold is at least 7 times greater than the mass of the melt of the test alloy filled therein, wherein the temperature of the homogeneous melt is at least 200 ℃ above the melting temperature prior to casting, wherein the temperature of the copper mold is 20 ℃, and wherein the crystalline fraction of a cylindrical molded part having an incremental diameter differing by 1mm and the cylindrical molded part thus produced is tested by means of dynamic differential scanning calorimetry.

5. The method of any one of claims 1-4, wherein the ingot has a size in three dimensions of space that is greater than a critical casting thickness.

6. The method of any one of claims 1-4, wherein the ingot comprises a crystallization fraction of at least 90% relative to weight as measured by DSC.

7. The method of claim 5, wherein the ingot comprises a crystallization fraction of at least 90% relative to weight as measured by DSC.

8. The method of any one of claims 1-4, wherein the ingot comprises a crystallization fraction of at least 95% relative to weight as measured by DSC.

9. The method of claim 7, wherein the ingot comprises a crystallization fraction of at least 95% relative to weight as measured by DSC.

10. The method of any one of claims 1-4, wherein the mold is selected from the group consisting of boron nitride, Y ₂ O ₃ And material coating of alumina.

11. The method of claim 9, wherein the mold is selected from the group consisting of boron nitride, Y ₂ O ₃ And material coating of alumina.

12. The method of any one of claims 1-4, wherein the ratio of melt weight to mold weight is 1:7 or less.

13. The method of any one of claims 1-4, wherein the temperature of the melt in step a) measured in degrees celsius is at least 20% above the melting temperature.

14. The method of claim 12, wherein the temperature of the melt in step a) measured in degrees celsius is at least 20% above the melting temperature.

15. Ingot of a bulk glass forming alloy comprising a critical casting thickness of at least 5mm, wherein the ingot has an extension in at least three dimensions of space that is greater than the critical casting thickness, characterized in that the ingot comprises a crystallization fraction of at least 90 wt.% as measured by DSC, wherein the ingot has no amorphous layer on the surface, wherein the critical casting thickness is determined by dynamic differential scanning calorimetry as follows: processing the test alloy in an electric arc to form a homogeneous melt and then pouring into a water cooled copper mold, wherein the mass of the copper mold is at least 7 times greater than the mass of the melt of the test alloy filled therein, wherein the temperature of the homogeneous melt is at least 200 ℃ above the melting temperature prior to casting, wherein the temperature of the copper mold is 20 ℃, and wherein the crystalline fraction of a cylindrical molded part having an incremental diameter differing by 1mm and the cylindrical molded part thus produced is tested by means of dynamic differential scanning calorimetry.

16. A method for producing a three-dimensional component from bulk metallic glass by means of a casting method, characterized in that an ingot (20) according to claim 15 is melted for the casting method.

17. The method of claim 16, wherein melting of the ingot takes no longer than 60 seconds.

18. The method of claim 16, wherein melting of the ingot takes no longer than 40 seconds.