Lamellar-forming grain boundary reaction related to age-hardening mechanism in an Au-Pt-Pd-In metal-ceramic alloy

• Published in: Gold Bulletin Vol. 47; no. 3; pp. 195 - 203
• Main Authors: Kim, Sung-Min, Kim, Hyung-Il, Jeon, Byung-Wook, Kwon, Yong Hoon, Seol, Hyo-Joung
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2014; World Gold Council; Springer Nature B.V
• Subjects: Ceramic metals; Chemical engineering; Chemical engineering research; Chemical properties; Chemical reactions; Chemistry and Materials Science; Gold alloys; Grain boundaries; Hardening; Lamellar structure; Materials research; Materials Science; Mechanical properties; Metallic Materials; Original Paper; Palladium; Platinum; Precipitates; Precipitation; Strength of materials; Tin; Precipitation; Au-Pt-Pd-In metal-ceramic alloy; Lamellar-forming grain boundary reaction; Age-hardening
• ISSN: 2190-7579; 1027-8591; 2190-7579
• DOI: 10.1007/s13404-014-0145-x

This study examined the relationship between the lamellar-forming grain boundary reaction and the change in hardness during the aging process of an Au-Pt-based metal-ceramic alloy composed of 76.6 Au–9.9 Pt–9.3 Pd–1.7 In–1.2 Ag–0.56 Sn (wt%) with minor ingredients. The phase decomposition of the parent Au-rich α phase occurred within a very short time (30 s) by aging at 550 °C after a solution-treatment at 950 °C due to the solubility limits of Au and Pt in each other, which initiated a lamellar-forming grain boundary reaction. The observed hardening was attributed to both the grain interior and grain boundary precipitate. On the other hand, the grain boundary precipitate comprising the fine lamellar structure caused more powerful hardening from the early stage of the aging process. The alternate layer of the grain boundary lamellar structure was composed of Pt-, In- and Sn-depleted Au-rich α 1 phase as well as precipitated Pt-, In- and Sn-concentrated β 1 phase. The extremely fine nature of the grain boundary lamellar structure supplied large amounts of inter-phase boundaries, which contained lattice strain by the difference in the lattice parameter between the α 1 and β 1 phases, resulting in hardening.