Feedstock barrels coated with insulating films for rapid discharge forming of metallic glasses

Patent metadata

Field	Value
Publication number	US-10213822-B2
Application number	US-201414501707-A
Country	US
Kind code	B2
Filing date	Sep 30, 2014
Priority date	Oct 3, 2013
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

The present disclosure is directed to feedstock barrels comprising thermally and electrically insulating films configured to be adjacent to a feedstock sample when it is loaded in the barrel for the process of shaping metallic glasses by rapid capacitor discharge forming (RCDF) techniques.

First claim

What is claimed is:

1. A rapid capacitor discharge forming (RCDF) apparatus for shaping metallic glasses, the apparatus comprising:
a feedstock barrel that comprises a feedstock barrel substrate and an insulating film disposed on the interior of the feedstock barrel substrate, wherein the feedstock barrel is configured to contain a metallic glass feedstock sample on the interior of the insulating film, wherein the feedstock barrel substrate comprises a metal;
a source of electrical energy configured to heat the metallic glass feedstock sample, said source electrically connected to at least one of a pair electrodes disposed at opposite ends of the feedstock barrel, said electrodes configured to discharge electrical energy sufficient to heat the metallic glass feedstock sample uniformly when the metallic glass feedstock sample is loaded into the feedstock barrel; and
a shaping tool disposed in forming relation to the metallic glass feedstock sample, the shaping tool configured to apply a deformation force sufficient to shape the metallic glass feedstock sample when heated to an article.

2. The RCDF apparatus of claim 1 , wherein the shaping tool is configured to cool the article at a rate sufficient to avoid crystallization.

3. The RCDF apparatus according to claim 1 , wherein the insulating film has an electrical resistivity of at least 1×10 5 μΩ-cm.

4. The RCDF apparatus according to claim 1 , wherein the insulating film has a dielectric strength of at least 5 kV/mm.

5. The RCDF apparatus according to claim 1 , wherein the insulating film has a dielectric breakdown voltage greater than 1000 V.

6. The RCDF apparatus according to claim 1 , wherein the insulating film has a thermal diffusivity less than 0.1 mm/s.

7. The RCDF apparatus according to claim 1 , wherein the insulating film has a thermal relaxation time of more than 0.05 s.

8. The RCDF apparatus according to claim 1 , wherein the insulating film has a thickness t equal to or less than 5% of the substrate thickness.

9. The RCDF apparatus according to claim 1 , wherein the insulating film has a thickness t equal to or less than 500 micrometers.

10. The RCDF apparatus according to claim 1 , wherein the insulating film comprises a material selected from the group consisting of a polymer, a cellulosic material, and a ceramic.

11. The RCDF apparatus according to claim 1 , wherein the electrically insulating film is adhered to the surface of the substrate by an adhesive.

12. The RCDF apparatus according to claim 1 , wherein the barrel substrate has a plane-strain fracture toughness of at least 30 MPa m 1/2 .

13. The RCDF apparatus according to claim 1 , wherein the barrel substrate has a yield strength of at least 30 MPa.

14. The RCDF apparatus according to claim 1 , wherein the barrel substrate comprises a material selected from the group consisting of low-carbon steels, stainless steels, nickel alloys, titanium alloys, aluminum alloys, copper alloys, brasses and bronzes, and pure metals such as nickel, aluminum, copper, and titanium.

15. The apparatus of claim 1 , wherein the insulating film has a thermal relaxation time t 2 /D>0.1 s.

16. The RCDF apparatus according to claim 3 , wherein the insulating film has an electrical resistivity at least 10 3 times higher than the electrical resistivity of the metallic glass feedstock sample.

17. The RCDF apparatus according to claim 10 , wherein the insulating film comprises a material selected from the group consisting of polytetrafluroethylene, phenolic resin, high-density polyethylene, low-density polyethylene, Kapton polyimide film, red insulating varnish, and paper.

18. A method of heating and shaping a metallic glass feedstock sample using an RCDF cycle comprising:
discharging electrical energy from a source of electrical energy across the metallic glass feedstock sample disposed in a feedstock barrel that comprises a feedstock barrel substrate and an insulating film, wherein the feedstock barrel substrate comprises a metal, wherein the insulating film is disposed on an interior surface of the feedstock barrel substrate, and the metallic glass feedstock sample is disposed on the interior of the insulating film of the feedstock barrel, to heat the metallic glass feedstock sample to a processing temperature between the Tg of the metallic glass and Tm of the metallic glass forming alloy, wherein the source of electrical enemy is electrically connected to at least one pair of electrodes, and wherein the at least one pair of electrodes are disposed at opposite ends of the feedstock barrel and connected to the metallic glass feedstock sample;
applying a deformational force to shape the heated metallic glass feedstock sample into an article; and
cooling the article to a temperature below the Tg of the metallic glass.

19. The method according to claim 18 , wherein the insulating film has thermal and chemical stability such that catastrophic failure is prevented during the RCDF cycle.

20. The method according to claim 19 , wherein the insulating film has electrical resistivity and dielectric strength such that negligible electrical current flows across the insulating film during the RCDF cycle.

Assignees

• Glassimetal Tech Inc
• Apple Inc

Inventors

• Lee David S
• Schramm Joseph P
• Demetriou Marios D
• Johnson William L

Classifications

• B21J1/06 Primary

  Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations {(B21J5/063 takes precedence)} · CPC title

• C21D1/40

  Direct resistance heating · CPC title

• B21J1/006 Primary

  Amorphous metal · CPC title

• B22D17/2023

  Nozzles or shot sleeves · CPC title