ROBUST INGOT FOR THE PRODUCTION OF COMPONENTS MADE OF METALLIC SOLID GLASSES

Abstract

A method for production of an ingot of a bulk glass-forming alloy, comprising the steps of: Providing a homogeneous melt of a bulk glass-forming alloy; casting the homogeneous melt into a casting mould, whereby the casting mould does not cool down below the glass-transition temperature of the alloy at the contact surface to the melt for at least 5 seconds; and cooling down the melt below the glass transition temperature of the bulk glass-forming alloy while obtaining the ingot.

Claims

1. A method for production of an ingot of a bulk glass-forming alloy, comprising the steps of: a. Providing a homogeneous melt of a bulk glass-forming alloy; b. casting the homogeneous melt into a casting mould, whereby the casting mould does not cool down below the glass-transition temperature of the alloy at the contact surface to the melt for at least 5 seconds; and c. cooling down the melt below the glass transition temperature of the bulk glass-forming alloy while obtaining the ingot.

2. The method according to claim 1, whereby the casting mould does not cool down below the glass-transition temperature of the alloy at the contact surface to the melt for at least 10 second.

3. The method according to claim 1, whereby the bulk glass-forming alloy has a critical casting thickness of 5 mm or more.

4. The method according to claim 1, whereby the size of the ingot in the three directions of space is larger than the critical casting thickness.

5. The method according to claim 1, whereby the ingot comprises a crystalline fraction of at least 90%, relative to the weight, as measured by means of DSC.

6. The method according to claim 1, whereby the ingot comprises a crystalline fraction of at least 95%, relative to the weight, as measured by means of DSC.

7. The method according to claim 1, whereby the casting mould is coated with a material selected from the group consisting of boron nitride, Y.sub.2O.sub.3, and aluminium oxide.

8. The method according to claim 1, whereby the ratio of the weight of the melt and the weight of the casting mould is 1:7 or less.

9. The method according to claim 1, whereby the temperature of the melt in step a) is at least 20% above the melting temperature, as measured in degrees centigrade.

10. An ingot of a bulk glass-forming alloy, comprising a critical casting thickness of at least 5 mm, whereby the ingot has an extension in at least three directions of space that is larger than the critical casting thickness, characterised in that the ingot comprises a crystalline fraction of at least 90% by weight, as measured by means of DSC.

11. A method for production of a three-dimensional component from a bulk metallic glass by means of casting processes, characterised in that an ingot (20) according to claim 10 is being melted for the casting process.

12. The method according to claim 11, whereby the melting of the ingot takes no longer than 60 seconds, in particular no longer than 40 seconds.

Description

EXAMPLES

[0079] The individual components were melted in an inert gas by means of inductive melting to form a homogeneous alloy with a composition of Zr.sub.52.5Ti.sub.5Cu.sub.17.9Ni.sub.14.6 Al.sub.10. Said alloy has a glass transition temperature of 403° C. A total of 80 g of the homogeneous alloy were heated by means of inductive heating in a melting crucible to a temperature above the melting temperature of the alloy (805° C.). The temperatures of the respective melts in each experiment are shown in Table 1. The casting mould was heated in a furnace to a temperature defined in Table 1 for each case. Subsequently, the respective homogeneous melt according to Table 1 was filled into a casting mould. The casting mould was cylindrical in shape and had an internal diameter of 19 mm. The temperature of the melt was measured continuously after filling it into the cylindrical casting mould. The measuring values of the temperature of the melt after 10 seconds in the casting mould are given in Table 1 for each case.

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 T.sub.melt[° C.] 1050 1100 1200  1250  1350  T.sub.casting mould[° C.]  50  50 250 400 600 Casting mould Copper Steel Steel Steel Steel Weight ratio 1:17 1:15 1:9 1:15 1:15 Coating of the casting none BN Y.sub.2O.sub.3 BN Al.sub.2O.sub.3 mould T.sub.casting mould after 10 s  150  150 410 420 approx. [° C.] 550 Ingot quality poor poor good good very good

[0080] Examples 1 and 2 in Table 1 are reference examples, Examples 3-5 are examples according to the invention. The quality of the cast ingots was assessed according to the following criteria: Cast parts of poor quality crack already while they cool down in the casting mould. Cast ingots of good quality stay intact when they are heated to the melting temperature at a power of 5 kW for at most 50 seconds. Ingots of very good quality additionally survive a drop test from a height of 30 cm onto a level steel plate, performed thrice, without cracking. It is evident from examples 1-5 that ingots, whose melt temperature after 10 seconds was above the glass transition temperature, were clearly more robust than ingots whose melt temperature was below that.

DESCRIPTION OF THE FIGURES

[0081] FIG. 1 shows a light microscope image showing the cross-section of an ingot that was produced according to Example 1 as a reference experiment. The bright regions in the cross-section, indicated by arrows in exemplary manner, show amorphous regions (arrow 1) surrounded by darker crystalline regions (arrow 2). Moreover, it is evident from FIG. 1 that the ingot is cracked.

[0082] FIG. 2 shows a light microscope image showing the cross-section of an ingot that was produced according to Example 4. The cross-section of an ingot according to Example 4 shows a homogeneous distribution of material without bright regions that would indicate amorphous phases.

[0083] FIG. 3 shows a magnification of the sample according to the invention from FIG. 2. The image shows the multi-crystalline structure of the ingot all the way into the marginal region of the cross-section.

[0084] FIG. 4 shows a schematic depiction of the process flow from the individual components of the bulk glass-forming alloy (5) to the component made of bulk metallic glass (40). The process flow goes through the following steps: Individual components of the bulk glass-forming alloy (5), homogeneous melt (10), ingot made of bulk glass-forming alloy (20), homogeneous melt of the bulk glass-forming alloy (30), and component made of bulk metallic glass (40).