SHAPED PARTS HAVING UNIFORM MECHANICAL PROPERTIES, COMPRISING SOLID METALLIC GLASS

Abstract

The invention relates to a method for producing a shaped part comprising a solid metallic glass. According to the method, a preform is shaped below the glass transition temperature and is then heated to a temperature above the glass transition temperature.

Claims

1) A method for the production of a shaped part comprising a bulk metallic glass, characterized by the following steps: a. providing a preform comprising a bulk metallic glass, b. repeated plastic deformation of the preform comprising a bulk metallic glass in several steps with a deformation Δd, wherein the temperature T.sub.1 of the preform is below the glass transition temperature of the bulk metallic glass, and c. heating the preform to a temperature T.sub.2 above the glass transition temperature and below the crystallization temperature to obtain a shaped part comprising a bulk metallic glass, wherein the plastic deformation in step b) takes place in such a way that the deformation Δd increases with an increasing number of steps.

2) The method according to claim 1, wherein the deformation Δd per deformation step is at least 1 μm, particularly at least 5 μm and at most 100 μm, particularly at most 50 μm.

3) The method according to claim 1, wherein the shaped part is heated in step c) in such a way that the flexural strength of the shaped part is not more than 15% below the value for the preform in step a).

4) The method according to claim 1, wherein the shaped part is plastically deformed in step b) in at least two and at most 300 steps.

5) The method according to claim 1, the heating in step c) taking place with the application of a pressure in the range from 1 to 600 MPa to the shaped part.

6) The method according to claim 1, wherein the pressure is applied between two plane-parallel surfaces.

7) The method according to claim 1, wherein the bulk metallic glass, by weight, has zirconium or copper as its main component.

8) The method according to claim 1, wherein the preform is formed after step b) and before step c).

9) The method according to claim 1, wherein the forming is carried out by hammering, deep drawing, or bending.

10) The method according to claim 1, wherein the repeated plastic deformation takes place with the aid of at least one roller.

11) The method according to claim 1, wherein the repeated plastic deformation takes place in each deformation step in the same direction or in alternating directions, particularly in directions orthogonal to one another.

12) (canceled)

13) (canceled)

14) A shaped part comprising a bulk metallic glass, wherein the shaped part has a diameter of at least 200 μm in at least one dimension, characterized in that the bulk metallic glass has a flexural strength of at most 15% which is below the flexural strength of the cast alloy.

15) The shaped part according to claim 14, wherein the shaped part has a diameter in at least two dimensions in the range of at least 200 μm.

16) The shaped part according to claim 14, the bulk metallic glass contain-ing zirconium as its main component by weight.

Description

[0065] FIG. 1 graphically represents a possible embodiment of the invention. The process steps are described from left to right. First, a preform made of solid metal glass is produced using a casting process (A). The preform produced is then deformed to a temperature T.sub.1 below the glass formation temperature by means of cold rolling (B). The preform is then heated to a temperature T.sub.2 above the glass transition temperature and below the crystallization temperature with the application of pressure (C). This is optionally followed by a polishing step (D) and optionally cutting the shaped part to a specific shape (E).

MEASUREMENT METHODS

[0066] DSC Measurement

[0067] The DSC measurements in the context of the invention are carried out in accordance with DIN EN ISO 11357-1:2017-02 and DIN EN ISO 11357-3:2018-07. The sample to be measured in the form of a thin disc or film (approx. 80-100 mg) is placed in the measuring device (NETZSCH DSC 404F1, NETZSCH GmbH, Germany). The heating rate is 20.0 K/min. Al.sub.2O.sub.3 is used as the crucible material. The heat flow is measured against an empty reference crucible, such that only the thermal behavior of the sample is measured.

[0068] The measurement method is carried out according to the following steps: [0069] a) The sample to be measured is heated at the above-mentioned heating rate to a temperature just below the melting temperature (T=0.75*Tm), and the heat flow measured. The measurement is completed when no more heat flow in connection with phase transitions can be measured. Particularly, the measurement is ended when an exothermic signal in connection with the crystallization process is completely detected. In the examples contained herein, measurements are performed from room temperature to about 600° C., for example. [0070] b) The sample is allowed to cool to room temperature. [0071] c) The sample is again heated to the same temperature at the same heating rate as in step a), and the heat flow is measured. [0072] d) The measurement from step c) is subtracted from the measurement from step a), which reveals the measurement difference. The enthalpy of crystallization, if any, can be determined from the difference measurement by forming an integral.

[0073] Glass Transition Temperature

[0074] In the context of the present invention, the glass transition temperature is measured according to ASTM E1365-03 as follows.

[0075] The sample to be examined is placed in a crucible in a DSC device (NETZSCH DSC 404F1, NETZSCH GmbH, Germany). The system is heated and cooled according to the following scheme, and the respective heat flow is measured in steps a) and c). [0076] a) heating to a temperature of 0.75*Tm at a heating rate of 20 K/min. [0077] b) cooling to room temperature [0078] c) heating to the same temperature as in step a) at the same heating rate [0079] d) cooling to room temperature

[0080] As a result of the experiment, the enthalpy is obtained as a function of the temperature for the sample. In step a), the amorphous sample is crystallized. In step c), the thermal behavior of the already completely crystallized sample is recorded.

[0081] In order to determine the glass transition temperature, the measurement from step c) is subtracted from the measurement from step a). The resulting curve includes an endothermic transition at a lower temperature and an exothermic signal at a higher temperature. The signal at a higher temperature corresponds to the crystallization process. The endothermic signal corresponds to the glass transition. In order to determine the glass transition temperature, a tangent line to the baseline is determined before the glass transition range (by linear fitting). A second tangent is determined at the turning point (corresponding to the peak value of the first derivative over time) of the glass transition range. The temperature value at the intersection of the two tangents indicates the glass transition temperature (T.sub.f according to AST 1356-03).

[0082] Crystallization Temperature

[0083] The crystallization temperature was determined by means of DSC in accordance with the DIN EN ISO standard 11357-3:2018-07. This standard is designed for polymers, but can be used analogously for metallic glasses. In the context of the invention, the crystallization temperature corresponds to the peak crystallization temperature T.sub.p,c as used in the standard mentioned herein. The heating rate was 20 K/min.

EXAMPLES

[0084] The alloy (Zr.sub.59.30Cu.sub.28.8Al.sub.10.4Nb.sub.1.5) was produced by melting the elements in a vacuum arc. A preform was made from the alloy produced by means of suction casting by pouring the homogeneous, liquid melt of the alloy into a copper casting mold. The copper mold was kept at room temperature. The casting obtained in the form of a tape had the dimensions 3×15×40 mm.

[0085] The cast part obtained in the form of a strip was rolled in a rolling mill at room temperature with increasing deformation steps to a thickness of 0.5 mm. The deformation steps started with a thickness reduction of 5 μm, and the rolling ended at a deformation Δd of 50 μm per deformation steps after 70 rolling processes.

[0086] The cold-rolled strip was then heated using a heated press below the crystallization temperature in the TTT diagram of the alloy for 60 seconds to achieve the desired flexural strength of approximately 2250 N/mm.sup.2 adjust.

[0087] According to the example described, 50 shaped parts were produced. For the components obtained, the stress-strain behavior was measured using a 3-point bending test (in accordance with DIN EN ISO 7438:2016-07). The results of the measurements are summarized in Table 1.

TABLE-US-00001 TABLE 1 Flexural strength Standard deviation [N/mm.sup.2] [N/mm.sup.2] (Number of (average) measured parts) Cast 2447 282 (10) Cast and rolled 1682 224 (6) Cast, rolled, TPF 2261 84 (10)

[0088] Table 1 summarizes the measured flexural strengths of the manufactured parts for different stages of manufacture and gives the standard deviation of the flexural strength over several parts for each processing step. It can be seen that shaped parts can be obtained using the method of the invention (3.sup.rd row), which parts have an average flexural strength of 2261 N/mm.sup.2 which is close to the initial value of the cast preform of 2447 N/mm.sup.2 while the homogeneity of the components (expressed by the lower standard deviation) has increased by a factor of 3.4 compared to the cast parts (row 1).