# US 2013/0153097 A1 · Gold alloy with improved hardness > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0153097 A1 - Document ID: US20130153097A1 - Status: Published application - Kind: A1 - Application number: 13/805,230 - Filed: 2011-06-16 - Published: 2013-06-20 - Earliest claimed: 2010-06-30 - Assignees: The Swatch Group Research and Development Ltd - Inventors: Jean-Francois Dionne; Stewes Bourban - Web page: https://patentgrep.com/patent/US20130153097A1 ## CPC - C22F 1/14: of noble metals or alloys based thereon - A44C 27/003: {Metallic alloys (alloys in general C22C)} - C22C 5/02: Alloys based on gold - C22F: CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass, C23F17/00) - A44C: PERSONAL ADORNMENTS, e.g. JEWELLERY; COINS - C22C: ALLOYS (treatment of alloys C21D, C22F) ## Abstract The invention concerns a gold alloy. It comprises at least 75% of gold, 0.5% to 2.1% of aluminium able to form precipitates with gold, an additional metal able to favour a stable face centred cubic structure and able to increase the solubility of aluminium in gold, and a precipitate selected to obtain a hardness of more than 250 HV. The selected precipitate of aluminium with gold is the aluminium and gold precipitate Al2Au5. It includes 0.5% to 2.1% of aluminium and a complement of additional metal including a majority of silver. The method of obtaining this alloy regulates the controlled growth of the precipitate during a structuring tempering treatment following dilution and hardening. The invention concerns the use of the aluminium and gold precipitate Al2Au5 for hardening a gold alloy. The invention concerns a timepiece or piece of jewellery including at least one component made of this type of alloy. ## Claims ### Claim at position 1 1-16. (canceled) ### Claim 17 A 3N 18 carat yellow gold-based alloy, comprising in weight percent: at least 75% of gold; from 0.5% to 2.1% of an aluminium metal capable of forming at least one precipitate with gold; from 20% to 25% of at least one first additional metal having an ability to favor a stable face centered cubic (FCC) structure and to increase high temperature solubility of the aluminum metal in the gold; 0% to 0.5% of at least one component affecting fluidity and grain size refinement of the alloy; and at least one aluminium and gold precipitate comprising Al2Au5 forming an intermetallic compound which provides the alloy with more than 250 HV hardness so as to improve structural hardening of the alloy. ### Claim 18 (depends on 17) The alloy according to claim 17, wherein the first additional metal is silver. ### Claim 19 (depends on 18) The alloy according to claim 18, wherein the first additional metal is 10% to 12.5% weight percent silver, and the alloy further comprises 10% to 12.5% weight percent of a second additional metal of lower concentration than that of the silver. ### Claim 20 (depends on 19) The alloy according to claim 19, wherein the second additional metal is copper. ### Claim 21 (depends on 17) The alloy according to claim 17, wherein a content of the at least one first additional metal is between 22.4% and 24.5%. ### Claim 22 (depends on 17) The alloy according to claim 17, wherein the at least one component affecting fluidity and grain size refinement of the alloy is selected from the group consisting of zinc, cobalt and iridium. ### Claim 23 (depends on 17) The alloy according to claim 17, comprising, as the only precipitate of aluminium and gold, the aluminium and gold precipitate comprising Al2Au5. ### Claim 24 A method for obtaining a gold-based alloy with improved hardness, the method comprising: (i) heat treating a mixture comprising: 0.5% to 2.1% of aluminium; at least 75% of gold; 20% to 25% of at least one first additional metal having an ability to favor a stable face centered cubic (FCC) structure and to increase high temperature solubility of the aluminum in the gold; and 0% to 0.5% of at least one component affecting fluidity and grain size refinement, to a temperature between 650° C. and 700° C. to form a heat treated mixture; then (ii) rapidly cooling the heat treated mixture by ambient temperature hardening to form a cooled mixture; (iii) tempering the cooled mixture at a temperature of between 200° and 250° C. to form at least one aluminium and gold precipitate comprising Al2Au5, said at least one precipitate being capable of inserting into the FCC structure of the at least one first additional metal and forming an intermetallic compound capable of imparting a desired hardness of more than 250 HV to a resulting gold-based alloy; (iv) maintaining the tempering for at least 60 minutes to grow the intermetallic compound in a controlled manner to obtain the resulting gold-based alloy with the desired hardness; and (v) cooling the resulting gold-based alloy at ambient temperature. ### Claim 25 (depends on 24) The method according to claim 24, wherein the rapid cooling (ii) is achieved by water hardening. ### Claim 26 (depends on 24) The method according to claim 24, wherein the at least one precipitate is a single precipitate. ### Claim 27 (depends on 24) The method according to claim 24, wherein the tempering (iii) occurs for at least 24 hours after the rapid cooling (ii). ### Claim 28 (depends on 24) The method according to claim 24, wherein the at least one first additional metal is silver. ### Claim 29 (depends on 24) The method according to claim 24, wherein the mixture further comprises at least one second additional metal in a lower concentration than that of the silver. ### Claim 30 (depends on 29) The method according to claim 29, wherein the second additional metal is copper. ### Claim 31 (depends on 24) The method according to claim 24, wherein the mixture comprises between 22.4% and 24.5% of the at least one first additional metal. ### Claim 32 (depends on 23) A timepiece or a piece of jewellery, comprising at least one component made of the gold-based alloy of claim 23. ### Claim 33 A method for hardening an 18 carat gold-based alloy, the method comprising forming at least one precipitate from aluminium and gold comprising Al2Au5 which forms an intermetallic compound within a gold-containing alloy and thereby imparts a resulting gold-based alloy with a hardness of more than 250 HV. ### Claim 34 (depends on 33) The method of claim 33, wherein: the gold-based alloy comprises: at least 75% of gold; 0.5% to 2.1% of aluminium; 20% to 25% of at least one additional metal selected from the group consisting of silver and copper, said additional metal having an ability to favor a stable face centered cubic (FCC) structure and to increase solubility of aluminium in gold; and 0% to 0.5% of at least one component affecting fluidity and grain size refinement of the gold-based alloy; the method further comprises inserting the intermetallic compound into the FCC structure during a solution heat treatment of a mixture comprising the gold, the aluminium, the at least one additional metal, and the at least one component if present; and the at least one additional metal is selected from the group consisting of aluminium, silver, chromium, copper, iron, hafnium, manganese, niobium, palladium, platinum, and vanadium. ### Claim 35 (depends on 34) The method of claim 34, wherein the at least one additional metal is silver. ### Claim 36 (depends on 35) The method of claim 35, wherein the alloy further comprises at least one second additional metal having a lower concentration than that of the silver. ### Claim 37 (depends on 36) The method of claim 36, wherein the at least one second additional metal is copper. ### Claim 38 (depends on 34) The method of claim 34, wherein the gold-based alloy comprises 22.4% to 24.5% of the at least one first additional metal. ### Claim 39 (depends on 34) The method of claim 34, where the Al2Au5 is the only aluminium and gold precipitate in the gold-based alloy.