US3117864A - Process for producing a worked gold alloy - Google Patents

Description

3,117,864- PRGCEdS FGR PRODUCDJG A WQRIQID GGLD ALLOY Edward G. Heath and Colin R. Yates, Kings Cross, London, England; said Heath asslgnor to Westinghouse llralte 8: Signal Company Limited, London, England, a company of Great Britain No Drawing. Filed Get. 20, 1961, Ser. No. 145,433 Claims priority, application Great Britain Oct. 2 1960 3 Claims. (Cl. 75-135) The present invention relates to an alloy of gold, silicon, and antimony having relatively good ductility and substantially uniform composition and a process for producing the same.

Heretofore it has been found highly difi-lcult to produce sound worked members comprising an alloy of gold, silicon and antimony. Gold and silicon alone have a tendency to segregate at the grain boundarie when attempts are made to alloy the same by melting and casting. When antimony also is present, the tendency to segregate is increased and many fissures are formed during casting of the ternary alloy. When the cast alloy is rolled or worked to shape, the fissures cause the member to crack thus rendering the final product useless.

The object of the present invention is to provide a sound worked alloy member comprising predetermined proportions of gold, silicon and antimony, the alloy being characterized by relatively good ductility and substantially uniform composition.

Another object of the invention is to provide a process for producing a sound Worked member comprising an alloy of gold, silicon and antimony having substantially uniform composition, the steps comprising melting the constituents of the alloy in a non-oxidizing atmosphere, rapidly cooling the alloy in a shallow mold, anneaing the alloy and hot rolling the same under non-oxidizing conditions.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

In accordance with the present invention and in attainment or" the foregoing objects, there is provided a sound worked member comprising an alloy having predetermined proportions of gold, silicon and antimony of substantially uniform composition and having relatively good ductility. The silicon and antimony may comprise from 0.01 to 10% each in the alloy. An alloy ingot is pre pared by heating desired proportions of each component or" the alloy in crucible tothe melting temperature of the alloy under an inert atmosphere or vacuum. The melt is then poured into a precooled shallow crucible in order to cause rapid solidification thereby sustantiall eliminating the tendency of the components in the alloy to segregate. The ingot is then remelted in a nonozddizing bath, such as, silicone oil at a temperature slightly in excess of the solidus temperature of the alloy. The second alloy melt is then poured into a thin walled metal mold immersed in an oil bath to cause the alloy to solidify very rapidly and to cool at rate of approximately 100 C. per second. The alloy casting is then annealed at an elevated temperature slightly below the melting temperature for a time suitable to obtain the desired grain structure. The alloy member is then rolled a temperature about or slightly above 300 until a thin foil of the order of 1 to 3 mils thick is obtained.

The rolled gold-silicon-antirnony alloy in foil pellet or other shapes i especially useful in making semiconductor devices wherein the antimony comprises an n-type doping material.

The following example is illustrative of the invention.

An alloy was prepared by melting 129 grams of gold, 3.995 grams of silicon and 0.1318 gram of antimony in ire States Patent 0 3,ll7,3bd Patented Jan. 14, 1984 a silica crucible While under an argon atmosphere at a pressure of 200 millimeters of mercury and a temperature of 1100 C. After a period of time sufiicient to melt the alloy and cause complete solution of the constituents, the temperature was lowered to about 1,000 C. and the alloy was poured into a water cooled stainless steel mold having internal dimensions of 1%. inch by inch by /2 inch.

Thi ingot was rernelted in a bath of silicone oil at a temperature of 380 C. (-10 C. in excess of the sol-idus temperature) and allowed to flow into a steel mold. The steel mold was immersed in a bath of silicone oil held at room temperature and the mold had a depth of approximately 0.06 inch and a wall thickness of less than 0.01 inch so that as the molten alloy is poured into the mold in the bath of oil, a very rapid solidification or" the alloy takes place owing to the rapid heat transfer to the oil bath. An estimated rate of cooling through the eutectic temperature (370 C.) was approximately 100 C. per second.

The alloy member was then annealed 30 minutes at 300 C. and then rolled at a temperature of from 300 C. to 320 C., oxidation of the alloy member being prevented by a thin film of silicone oil which was allowed to adhere to the alloy member surface. The alloy member is then annealed again for a period or" 20 minutes at 300 C. and subsequently rolled, the sequence being continued until a foil of approximately 0.002 inch thickness was obtained. By this means, a length of foil in excess of 3 feet was successfully prepared.

it is intended that the above description be interpreted as illustrative and not limiting.

We claim as our invention:

1. A process for producing a worked member comprising an alloy comprising from 0.01% to 10% of silicon, from 0.01% to 10% antimony and the balance being gold, of substantially uniform composition and having relative- 1y good ductility, the steps comprising melting the constituents of the alloy in a crucible in an inert atmosphere at an elevated temperature to insure complete dissolution of said constituents, rapidly solidifying the melt to preclude segregation of the constituents the grain boundaries, annealing the soli ified member and hot working the member under non-oxidizing conditions.

2. A process for producing a worked member comprising an alloy comprising from 0.01% to 10% of silicon, from 0.01% to 10% antimony and the balance being gold, of substantially unifonm composition and having relatively good ductility, the steps comprising melting the constituents of the alloy in a. silicon crucible under an atmosphere of pure dry argon to insure compl te dissolution of said constituents, rapidly solidifying the melt in a bath of silicone oil to preclude segregation of the constituents at the grain boundaries, anneadng the solidified member at a temperature of about 300 C. for about 30 minutes and hot rolling the member at a temperature of iron 300 C. to 320 C.

3. A process for producing a worked member comprising an alloy comprising from 0.01% to 10% of silicon, from 0.01% to 10% of antimony and the balance gold substantially uniform composition and having relatively good ductility, the steps com-prising melting the constituents of the alloy in a silica crucible under an atmosphere of pure dry argon at a pressure or" about 200 mm. of mercury and a temperature of about 1100 C. solidifying the melt in a precooled mould, remelting the solidified member in a bath of silicone oil at a temperature of about 380 C., rapidly solidifying the melt in a bath of silicone oil to preclude segregation of the constituents at the grain boundaries, annealing the member for about 30 minutes and rolling the same at a temperature of about 30 C. in a silicone oil bath and con- Metals and Solidifications, A.S.M., Cleveland, pp. 201 and 203.

Form et al.: solidification of Metals, Modern Castings, vol. 37, April 1960, pp. 151 and 153.

Smith: Principles of Physical Metallurgy, Harper & Bros, publishers, N.Y., 1956, page 324.

Beck: Technology of Magnesium and Its Alloys, Hughes & Co. Ltd, London, 1940, page 322.

Claims (1)

1. A PROCESS FOR PRODUCING A WORKED MEMBER COMPRISING AN ALLOY COMPRISING FROM 0.01% TO 10% OF SILICON, FROM 0.01% TO 10% ANTIMONY AND THE BALANCE BEING GOLD, OF SUBSTANTIALLY UNIFORM COMPOSITION AND HAVING RELATIVELY GOOD DUCTILITY, THE STEPS COMPRISING MELTING THE CONSTITUENTS OF THE ALLOY IN A CRUICIBLE IN AN INERT ATMOSPHERE AT AN ELEVATED TEMPERATURE TO INSURE COMPLETE DISSOLUTION OF SAID CONSTITUENTS, RAPIDLY SOLIDIFYING THE MELT TO PRECLUDE SEGREGATION OF THE CONSTITUENTS THE GRAIN BOUNDARIES, ANNEALING THE SOLIDIFIED MEMBER AND HOT WORKING THE MEMBER UNDER NON-OXIDIZING CONDITIONS.