Methods and apparatus for using large inertial body forces to identify, process and manufacture multicomponent bulk metallic glass forming alloys, and components fabricated therefrom

• US 6,695,936 B2
• Filed: 11/14/2001
• Issued: 02/24/2004
• Est. Priority Date: 11/14/2000
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Johnson, William L.
• Primary Examiner(s): KASTLER, SCOTT R
• Application Number:
  US09/991,802
• Publication Number:
  US 20020112790A1
• Time in Patent Office: 832 Days
• Field of Search: 148/508, 148/403, 148/538, 148/539, 753/75, 753/84, 753/86, 164/118, 164/290
• US Class Current: 148/508
• CPC Class Codes: B22D 13/04 of shallow solid or hollow bodies, e.g. wheels or rings, in moulds rotating around their axis of symmetry

Abstract

To identify and manufacture metallic glass forming alloys, large inertial forces or “g”-forces are used to sequentially separate crystalline phases (particles) as they sequentially form and grow in a molten alloy during gradual cooling of the alloy below its liquidus temperature. These forces physically remove and isolate the actual crystalline particles from the remaining liquid as they are formed. Under the influence of a large g-force, this is accomplished by rapid and efficient sedimentation and stratification. Further contamination and nascent solid “debris” in the form of oxides, carbides, or other foreign particles can be removed from the molten alloy using the same sedimentation/stratification technique. Finally, a method of efficiently cooling and solidifying the final low melting stratified and decontaminated liquid into a solid glass component is proposed which utilizes convective heat transport by a cooling gas. The result is a vitrified bulk metallic glass component of near net shape.

Claims

1. A method of identifying the lowest melting eutectic composition of an alloy having “

n”

phases, where n≧

2, the method comprising;

providing an arbitrary starting alloy;

heating the alloy until it is substantially molten;

subjecting the molten alloy to a large inertial force for a period of time while maintaining its temperature above the alloy'"'"'s melting point;

lowering the temperature of the alloy below the melting point while subjecting the alloy to a large inertial force, thereby causing nucleation and growth of a first solid phase within surrounding liquid, the first solid phase being subjected to the inertial force such that the first solid phase moves upward or downward within the surrounding liquid by sedimentation;

further lowering the temperature of the alloy while subjecting the alloy to said inertial force, thereby causing further nucleation and growth of additional solid phases, the additional solid phases being subjected to the inertial force such that the additional solid phases move upward or downward within the surrounding liquid by sedimentation, wherein the temperature is further lowered until the alloy is substantially completely solidified; and

identifying the last solid phase to solidify, the last solid phase being stratified in a layer between earlier solidified solid layers, the last solid phase having the lowest melting eutectic composition.

2. The method of claim 1, wherein the arbitrary starting alloy has a composition lying in the n-phase coexistence region when the alloy is in a low temperature portion of the phase diagram.

3. The method of claim 1, wherein subjecting the alloy to an inertial force comprising subjecting the alloy to a centripetal acceleration in a rotating apparatus.

4. The method of claim 3, wherein subjecting the alloy to a centripetal acceleration comprises placing the alloy in a centrifuge.

5. The method of claim 3, wherein the centripetal acceleration is about 1 to 10⁶ g'"'"'s

6. The method of claim 3, wherein the centripetal acceleration is about 10⁵-10⁶ g'"'"'s.

7. The method of claim 1, wherein identifying the last solid phase to solidify comprises using a method selected from the group consisting of X-ray diffraction, X-ray spectroscopy, EDS and Auger spectroscopy to identify the composition of the last solid phase.

8. The method of claim 1, further comprising cooling the alloy prior to identifying the last solid phase.

9. The method of claim 1, wherein lowering the temperature of the alloy from the molten state until the last solid phase solidifies occurs over a period of about 1 minute to 10 hours at a cooling rate of about 0.001°

C./second to about 10°

C./second.

10. The method of claim 1, wherein the alloy solidifies into a mixture having three or more phases.

11. The method of claim 1, wherein at least some of the solid phases include impurity phases, and wherein the last solid phase to solidify has fewer impurities relative to the remaining alloy.

12. The method of claim 11, wherein the impurity phases include oxide, carbide or nitride particles.

13. A method of producing a bulk sample of a lowest melting eutectic composition of an alloy, the method comprising:

providing an arbitrary starting alloy;

heating the alloy until it is substantially molten;

subjecting the alloy to a centripetal acceleration for a period of time while maintaining its temperature above the melting point;

lowering the temperature of the alloy while subjecting the alloy to a centripetal acceleration, the lowering of the temperature causing nucleation and growth of a first solid phase within surrounding liquid, the first solid phase being subjected to the centripetal acceleration such that the first solid phase moves upward or downward in the surrounding liquid by sedimentation;

further lowering the temperature of the alloy while subjecting the alloy to said acceleration, the further lowering of the temperature causing further nucleation and growth of additional solid phases, the additional solid phases being subjected to the acceleration such that the additional solid phases move upward or downward in the surrounding liquid by sedimentation, wherein the temperature is further lowered until the alloy is substantially completely solidified; and

casting a bulk sample of alloy using material taken from the last solid phase to solidify.

14. The method of claim 13, wherein the arbitrary starting alloy has a composition lying in n-phase coexistence region when the alloy is in a low temperature portion of the phase diagram.

15. The method of claim 13, wherein subjecting the alloy to a centripetal acceleration comprises placing the alloy in a centrifuge or spinning rotor assembly.

16. The method of claim 13, wherein the centripetal acceleration is about 1 to 10⁶ g'"'"'s.

17. The method of claim 13, wherein the centripetal acceleration is about 10³-10⁶ g'"'"'s.

18. The method of claim 13, wherein the centripetal acceleration is about 10⁵-10⁶ g'"'"'s.

20. The method of claim 13, wherein the solid alloy in equilibrium has three or more phases.

21. The method of claim 13, wherein casting a bulk sample of alloy comprises using the last solid phase to solidify as feed stock for casting.

22. The method of claim 13, wherein casting a bulk sample of alloy comprises directly casting at least a portion of the alloy containing the last solid phase to solidify into a mold.

19. A method of producing a bulk sample of a lowest melting eutectic composition of an alloy, the method comprising:

providing an arbitrary starting alloy;

heating the alloy until it is substantially molten;

subjecting the alloy to a centripetal acceleration for a period of time while maintaining its temperature above the melting point;

lowering the temperature of the alloy for a period of about 1 minute to ten hours while subjecting the alloy to a centripetal acceleration, the lowering of the temperature causing nucleation and growth of a first solid phase within surrounding liquid, the first solid phase being subjected to the centripetal acceleration such that the first solid phase moves upward or downward in the surrounding liquid by sedimentation;

further lowering the temperature of the alloy while subjecting the alloy to said acceleration, the further lowering of the temperature causing further nucleation and growth of additional solid phases, the additional solid phases being subjected to the acceleration such that the additional solid phases move upward or downward in the surrounding liquid by sedimentation, wherein the temperature is further lowered until the alloy is substantially completely solidified; and

casting a bulk sample of alloy using material taken from the last solid phase to solidify.

23. A method of forming a metallic glass alloy, comprising:

melting a mulitcomponent alloy;

cooling the molten alloy in the presence of a centripetal acceleration, until a last solid phase solidifies; and

subsequently forming an amorphous metal by cooling the last solid phase to solidify from an elevated temperature to ambient temperature at a rate sufficient to suppress crystallization.

24. The method of claim 23, which the multicomponent alloy contains two primary components.

25. The method of claim 23, which the multicomponent alloy contains three or more primary components.

26. The method of claim 23, comprising solidifying the alloy in the presence of a g field of between about 1 and 10⁶ g'"'"'s.

27. The method of claim 23, wherein the alloy is contained in a centrifuge.

28. The method of claim 23, wherein the alloy is solidified at a rate of between about 0.001°

C./second and 10°

C./second.

29. The method of claim 23, further comprising using a portion of the solidified alloy as a feed stock for casting.

30. The method of claim 23, wherein the last solid phase to solidify is the lowest melting eutectic composition of the alloy.

31. The method of claim 23, wherein the alloy is contained in a sample column.

32. A method forming a metallic glass alloy, comprising:

melting a mulitcomponent alloy;

cooling the molten alloy in the presence of a centripetal acceleration, until a last solid phase solidifies; and

subsequently forming an amorphous metal by cooling the last solid phase to solidify from an elevated temperature to ambient temperature at a rate sufficient to suppress crystallization, wherein the alloy is contained in a sample column which includes a gate for removing at least a portion of the alloy.

33. The method of claim 32, wherein the gate is located adjacent to a portion of the alloy which, upon solidification, contains relatively fewer impurities than the remaining alloy.

34. A method of forming a purified, multicomponent bulk metallic glass forming alloy, comprising:

(a) melting a sample alloy at an elevated temperature;

(b) subjecting the molten alloy to a centripetal acceleration while holding it above the melting point for a period of time;

(c) solidifying the alloy by lowering the temperature of the alloy while continuing to subject the alloy to a centripetal acceleration, the solidified alloy having a portion separated from the remaining alloy having a lowest melting eutectic composition;

(d) isolating the portion of the alloy having the lowest melting eutectic composition;

(e) re-melting the portion of the alloy having the lowest melting eutectic composition at an elevated temperature, while subjecting this portion to a centripetal acceleration; and

(f) subsequently cooling the portion of the alloy having the lowest melting eutectic composition while subjecting the portion to a centripetal acceleration, the cooled alloy having a portion with relatively fewer impurity phases than the remaining alloy.

35. The method of claim 34, wherein the portion of the alloy having the lowest melting eutectic composition is contained in a sample column.

36. The method of claim 35, wherein the sample column includes a gate adjacent that portion of the cooled alloy having relatively fewer impurity phases.

37. The method of claim 36, further comprising removing that portion of the cooled alloy having relatively fewer impurity phases from the sample through the gate, and transferring the removed portion to a mold or die.