CN-116609160-B - Metallographic structure display method of gold-based alloy

Abstract

The invention provides a gold-based alloy metallographic structure display method which comprises the steps of taking a gold-based alloy as an anode, carrying out electrolytic etching in electrolyte composed of hydrochloric acid, nitric acid and absolute ethyl alcohol, then cleaning the surface of the obtained gold-based alloy to obtain the gold-based alloy subjected to electrolytic etching, soaking the gold-based alloy subjected to electrolytic etching in ammonia water, then cleaning the surface of the obtained gold-based alloy, obtaining the preliminarily treated gold-based alloy after the surface is dried, immersing the preliminarily treated gold-based alloy in corrosive liquid composed of chromium trioxide saturated aqueous solution, hydrochloric acid and distilled water, then cleaning the surface of the obtained gold-based alloy, and completing the metallographic structure display of the gold-based alloy after the surface is dried, thereby greatly facilitating the observation of the metallographic structure of the gold-based alloy and being beneficial to obtaining gold-based alloy products meeting the performance requirements.

Inventors

• WANG AIJUAN
• YAN SIYU
• MA XIAOLONG
• LIU RONG
• RU YAN

Assignees

• 西安理工大学

Dates

Publication Date

20260512

Application Date

20230523

Claims (6)

1. 1. The metallographic structure display method of the gold-based alloy is characterized by comprising the following steps of: S1, taking a mechanically polished gold-based alloy with a bright surface and no dirt or scratch as an anode, carrying out electrolytic etching in an electrolyte with the temperature of 0-30 ℃ composed of hydrochloric acid, nitric acid and absolute ethyl alcohol, wherein the direct current voltage during electrolytic etching is 10-30V, the time is 1-20S, hydrochloric acid accounts for 2.5-5% of the volume of the electrolyte, nitric acid accounts for 5-10% of the volume of the electrolyte, and then washing the obtained gold-based alloy surface with water to obtain the gold-based alloy after electrolytic etching; The gold-based alloy is obtained by the following processes that mechanical polishing is automatic polishing, the rotating speed is 1000-1400 rpm, diamond polishing paste and tap water are used for polishing, polishing cloth is flocking fabric, and the time is 5-12 min; S2, soaking the gold-based alloy subjected to electrolytic etching in ammonia water with the concentration of 25% -28% for 10-30 seconds, then cleaning the surface of the obtained gold-based alloy with water, and obtaining the primarily treated gold-based alloy after the surface is dried; S3, immersing the primarily treated gold-based alloy in an etching solution composed of a chromium trioxide saturated aqueous solution, hydrochloric acid and distilled water for 5-15S, wherein the chromium trioxide saturated aqueous solution accounts for 5-15% of the volume of the etching solution, the hydrochloric acid accounts for 2.5-10% of the volume of the etching solution, then cleaning the obtained gold-based alloy surface with water, and finishing metallographic structure display of the gold-based alloy after the surface is dried.
2. 2. The method for displaying a metallographic structure of a gold-based alloy according to claim 1, wherein the stainless steel plate in S1 is used as a cathode, and the anode and the cathode are respectively connected with the anode and the cathode of an electropolishing corrosion apparatus.
3. 3. The method according to claim 1, wherein in S1, the mass fraction of hydrochloric acid is 37% and the mass fraction of nitric acid is 68%.
4. 4. The method for displaying metallographic structure of gold-base alloy according to claim 1, wherein in S2 and S3, alcohol is used to wipe the surface of the cleaned gold-base alloy, and finally the alloy is dried.
5. 5. The method for displaying a metallographic structure of a gold-based alloy according to claim 1, wherein in S3, the chromium trioxide saturated aqueous solution, hydrochloric acid and distilled water are stirred uniformly to obtain a corrosive liquid.
6. 6. The method for displaying a metallographic structure of a gold-based alloy according to claim 1, wherein in S1, hydrochloric acid, nitric acid and absolute ethyl alcohol are stirred uniformly to obtain an electrolyte.

Description

Metallographic structure display method of gold-based alloy Technical Field The invention belongs to the technical field of metal surface chemistry and electrochemical treatment, and particularly relates to a metallographic structure display method of a gold-based alloy. Background Electrical contact materials are widely used in the electrical industry, the performance of which directly affects the life and safe operation of switching devices. Current conversion is an essential component of the power supply and distribution process in electrical power systems, where any electrical power system must transfer electrical signals or energy from one conductor to another, where the connection of conductors to conductors, i.e., electrical contacts, is often a major impediment to electrical signals or energy transfer, often subject to physical and chemical processes such as mechanical, electrical, thermal, environmental, and the like. Therefore, for the electric contact material, it is required that the applied alloy has good electric conduction and thermal conductivity, corrosion resistance and wear resistance, high chemical stability, and the like. Gold-based alloys are widely used as one of the most widely used alloy electrical contact materials, and have excellent electrical contact characteristics due to good chemical stability, and also have very low yield points and elastic moduli, so they are widely used as precision electrical contact materials or sliding electrical contact materials under low contact pressure and small load. The gold-based alloy electric contact materials which are practically applied at present mainly comprise AuAg 20、AuAg20Cu5、AuPt10、AuAg25Pt5 and are mainly applied to integral and composite rivets, copper alloy upper cladding layers and contact rivets. In addition, the gold-based alloy has good application in the fields of dental alloy, gold for ornaments and the like. As gold-based alloys have found very wide application in electrical contact materials, ornamental materials and dental alloy materials, the requirements for such products are also increasing. In the preparation process of the product, the difference of alloy material components and the adjustment of heat treatment process parameters often affect the microstructure of the material, so that the performance of the alloy material is affected, and therefore, the metallographic structure of the gold-based alloy must be observed in order to obtain the product meeting the performance requirement. In general, the corrosion of gold-based alloys is to directly soak the alloy surface in a corrosive liquid, such as Xia, wang Shuming, yang Yin, etc. A novel metallographic corrosive agent [ J ]. Physical and chemical examination (physical division) of high purity gold, 2020,56 (05): 21-22+26. A metallographic corrosion method for high purity gold is described in the foregoing, which is to soak the sample surface in two mixed aqueous solutions of aqua regia, ferric chloride, hydrochloric acid and hydrogen peroxide, respectively, and corrode for 20s at room temperature, but after the two corrosive liquids are tested, the metallographic structure effect obtained after corrosion is found to be not good because a certain proportion of silver and copper exist in the gold-based alloy components to influence the corrosion effect. In Xu Kun. Metallographic erosion behavior of gold, silver and palladium and alloys thereof in Cr 6+ containing reagent [ J ]. Physical and chemical examination (physical handbook), 1999 (07): 308-309. In the corrosion process of gold and alloys thereof, the sample surface is directly dipped in cotton and wiped at room temperature and then directly soaked in mixed solution of nitric acid, hydrochloric acid and saturated chromic anhydride solution for several seconds to several minutes, but when alloys Au-5Ag-20Cu and Au-20Ag-10Cu are corroded by adopting the corrosion method, the grain boundaries of tissues cannot be clearly displayed, and the same result is obtained even after the formula is adjusted. The method for displaying the metallographic structure of alloy AuAgCuMnGd is determined in Yang Yulu, ma Yonghua, auAgCuMnGd, noble metal, 1982 (03): 47-49, specifically by heating and etching with a mixed solution of potassium cyanide and ammonium persulfate at high concentration, and in Japanese patent publication No. Pei Zhuo, metallographic etching handbook [ M ]. Scientific press, 1982, electrolytic etching of gold and its alloys in a mixed solution of potassium cyanide and distilled water is also mentioned, and these two methods are difficult to be widely used because cyanide is extremely toxic. In addition, in publication number CN110907258a, publication number 2020-03-24, chinese patent entitled "electrolytic corrosion method for gold metallography" describes an electrolytic corrosion method for gold, in which the electrolytic corrosion solution is a mixed solution of hydrogen peroxide and hydrochloric acid, bu