ผลของสังกะสีและซิลิคอนต่อโครงสร้างจุลภาค สมบัติทางกลและความต้านทานการหมองของโลหะผสมเงินเกรด 940

• Main Author: จิรัฐิติกาลผ่องศรี หิรัญเกิด
• Other Authors: เอกสิทธิ์ นิสารัตนพร
• Format: Theses and Dissertations
• Language: Thai
• Published: จุฬาลงกรณ์มหาวิทยาลัย 2007
• Subjects: สังกะสี; ซิลิกอน; โลหะผสมเงิน; โลหะ > สมบัติทางกล; โลหะ > โครงสร้างจุลภาค; Zinc; Silicon; Silver alloys; Metals > Mechanical properties; Metals > Microstructure
• Online Access: https://digiverse.chula.ac.th/Info/item/dc:44683
• Institution: Chulalongkorn University

The objective of this research is to investigate the effect of zinc and silicon in silver alloys grade 940 on their microstructure, mechanical properties, tarnish resistance, corrosion resistance, homogenization, reduction of area and annealing. This is ultimately to determine the suitable zinc and silicon content of silver alloys grade 940 for the jewelry industry. The experimental alloys were divided into 3 groups, first group contains zinc and copper, second group consists of zinc, copper and fixed silicon 0.02 wt% and the last one group was zinc, copper and silicon 0.036-0.065 wt% alloy. The microstructure consists of both silver-rich phase, as a matrix, and eutectic structure. The amount of zinc and silicon found in the in the eutectic structure is higher than those in matrix. The amount of eutectic structure is decreased by increasing zinc content. Nevertheless enhancing properties with zinc additive, yield strength and hardness decreased significantly but elongation increased. The tarnish resistance was found to be improved when the amount of 0.036%Si - 3.23%Zn - 2.30%Cu - Balance of Ag. The tarnish films were studied quantitatively using a spectrophotometer. Homogization at 750 ℃ for 30 and 60 minutes. Therefore, decrease tensile strength. In contrast, hardness and elongation of the alloys were increasing. Potentiodynamic anodic polarization technique was applied to measure the corrosion potentials (E[subscript com]) and corrosion current density (I[subscript com]). In 1% sodium chloride solution the increasing of zinc and silicon content not only promoted the noble shift in corrosion potentials but also reduced passive current density. However, in 1% sodium chloride solution saturated with hydrogen sulfide (H₂S), the passive region could not be observed.