Production of amorphous metallic foam by powder consolidation

• US 20070048164A1
• Filed: 01/23/2006
• Published: 03/01/2007
• Est. Priority Date: 01/21/2005
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Johnson, William, Schroers, Jan, Demetriou, Marios, Veazey, Christopher
• Granted Patent: US 7,597,840 B2
• Time in Patent Office: Days
• US Class Current: 419/2
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 3/02 Compacting only
• CPC Class Codes: B22F 3/1125 involving a foaming process
• CPC Class Codes: B22F 9/002 amorphous or microcrystalline
• CPC Class Codes: Y10T 428/12479 Porous [e.g., foamed, spongy, cracked, etc.]

Abstract

The formation of amorphous porous bodies and in particular to a method of manufacturing such bodies from amorphous particulate materials. The method allows for the control of the volume fraction as well as the spatial and size distribution of gas voids by control of the size distribution of the powder particulates. The method allows for the production of precursors of unlimited size, and because of the softened state of the amorphous metals used in the method possess visco-plastic properties, higher plastic deformations can be attained during consolidation as well as during expansion.

Claims

1. A method of forming an amorphous metal foam formed of an amorphous metal powder comprising:

mixing at least one amorphous metal powder and at least one gas-splitting propellant powder into a propellant filled amorphous metal powder mixture;

arranging the particles of the mixture to form defined voids;

compacting the mixture in such fashion that the metal particles are permanently bonded to one another to form a gas-tight seal for the gas particles of the propellant, the mixture being compacted at a compacting temperature sufficient to allow for the bonding of the mixture, but below the crystalline transition temperature of the amorphous metal, and for a duration not exceeding the time for the crystalline transformation of said amorphous metal at the compacting temperature

cooling the compacted mixture at a cooling rate sufficient to retain the amorphous state of the mixture;

expanding the compacted mixture to form a foam material, said expansion being conducted at an expansion temperature below the crystalline transition temperature of the metal powder, but sufficiently high to allow bubble expansion, at the lowest possible ambient pressure, and for a duration not exceeding the time for the crystalline transformation to take place; and

cooling the expanded foam material in order to retain the amorphous state of the material.

2. The method according to claim 1 wherein the temperature and pressure during hot-compacting avoids the decomposition of the propellant.

3. The method according to claim 1 wherein the temperature and pressure during hot-compacting triggers the decomposition of the propellant.

4. The method according to claim 1 wherein the expansion temperature is above the crystalline transition temperature of the amorphous metal, and further comprising the step of heating the compacted body above the melting temperature of the alloy such that the alloy melts, and then rapidly cooling the melt to prevent recrystallization.

5. The method according to claim 1 wherein the action of heat and the action of pressure are simultaneously suspended at the end of the hot-compacting process and the complete cooling of the metal body takes place without the influence of pressure.

6. The method according to claim 1 wherein the powder mixture has added to it high-strength reinforcing components.

7. The method according to claim 6 wherein the hot-compacting step is followed by aligning the reinforcing components in a preferential direction.

8. The method according to claim 1 wherein the method is selected from the group consisting of:

hot pressing, hot extrusion, hot forging, hot rolling and dyna-packing.

9. The method according to claim 1 wherein the amorphous metal is selected from the group consisting of alloys based on:

Zr, Ti, Al, Fe, La, Cu, Mg, Pt and Pd.

10. The method according to claim 1 wherein at least two different propellant powders with different decomposition temperatures are used.

11. The method according to claim 1 wherein the hot-compacting takes place in a mold such that the powder mixture is completely or partially surrounded by a propellant-free metal or metal powder.

12. The method according to claim 1 wherein the compacting is accomplished by extrusion molding, with the powder mixture being piled against a propellant-free metal piece.

13. The method according to claim 1 wherein a porous metal body is made by heating the metal body to a temperature below the crystallization temperature of the amorphous metal, followed by cooling of the body thus foamed.

14. The method according to claim 1 wherein a porous metal body is made by heating the metal body to a temperature below the crystalline temperature of the amorphous metal but above the visco-elastic temperature of the metal, followed by cooling of the body thus foamed.

15. The method according to claim 1 wherein a porous metal body is made by heating the metal body to a temperature below the crystalline temperature of the amorphous metal, whereby during foaming of the metal body, different temperature and time values are used as a function of the density of the metal body to be produced, followed by cooling of the body thus foamed.

16. The method according to claim 1 wherein a porous metal body is made by heating the metal body to a temperature below the crystalline temperature of the amorphous metal, with the heating rate being between 1°

and 5°

C./sec, followed by cooling of the body thus foamed at a rate which is so high relative to the volume of the foamed body that further foaming is interrupted.

17. The method according to claim 1 wherein the propellant is selected from the group consisting of:

water vapor-releasing agents, hydrogen-releasing agents, carbon monoxide-releasing agents, carbon dioxide-releasing agents, and nitrogen-releasing agents

18. The method of claim 1, wherein the metal powder is in an initial crystalline state, and further comprising the step of heating the compacted body above the melting temperature of the alloy such that the alloy melts, and then rapidly cooling the melt to prevent recrystallization.

19. A method of forming an amorphous metal foam formed of an amorphous metal powder comprising:

arranging the particles of an amorphous metal powder to form defined voids;

placing the powder in a gas-tight chamber, and pressurizing the chamber with a pressurizing gas at a pressure sufficient to compact and bond the powder together around discrete gas-containing pores;

heat treating the compacted powder to increase the pressure of the gas within the gas-containing pores at a compacting temperature sufficient to allow for the visco-plastic deformation of the powder, but below the crystalline transition temperature of the amorphous metal, and for a duration not exceeding the time for the crystalline transformation of said amorphous metal at the compacting temperature

cooling the compacted powder at a cooling rate sufficient to retain the amorphous state of the powder;

expanding the compacted powder to form a foam material, said expansion being conducted at an expansion temperature below the crystalline temperature of the metal powder, but sufficiently high to allow visco-plastic deformation during bubble expansion, at the lowest possible ambient pressure, and for a duration not exceeding the time for the crystalline transformation to take place; and

cooling the expanded foam material in order to retain the amorphous state of the material.

20. The method according to claim 19 wherein the expansion temperature is above the crystalline transition temperature of the amorphous metal, and further comprising the step of heating the compacted body above the melting temperature of the alloy such that the alloy melts, and then rapidly cooling the melt to prevent recrystallization.

21. The method of claim 19 wherein the pressure of the chamber is from vacuum to over 100 atm.

22. The method of claim 19 wherein the pressure within the gas-filled pores is from about vacuum to over 2000 atm.

23. The method of claim 19 wherein the gas is selected from the group consisting of:

helium, argon, air, nitrogen, and hydrogen.

24. The method according to claim 19 wherein the compacting method is selected from the group consisting of:

hot pressing, hot extrusion, hot forging, hot rolling and dyna-packing.

25. The method according to claim 19 wherein the amorphous metal is selected from the group consisting of alloys based on:

Zr, Ti, Al, Fe, La, Cu, Mg, Pt and Pd.