Age-hardening associated with grain boundary precipitation in a commercial dental gold alloy

• Published in: Journal of oral rehabilitation 1999-03, Vol.26 (3), p.215-222
• Main Authors: Kim, H. I., Jang, M. I., Kim, M. S.
• Format: Article
• Language: English
• Subjects: Chemical Phenomena; Chemical Precipitation; Chemistry, Physical; Copper - chemistry; Dental Casting Investment - chemistry; Dentistry; Gold - chemistry; Gold Alloys - chemistry; Hardness; Humans; Materials Testing; Metallurgy; Microscopy, Electron, Scanning; Platinum - chemistry; Silver - chemistry; Surface Properties; Time Factors; X-Ray Diffraction
• ISSN: 0305-182X; 1365-2842
• DOI: 10.1046/j.1365-2842.1999.00371.x

The aim of this study was to make clear the age‐hardening mechanism in a dental high carat gold alloy. For this purpose, age‐hardening behaviour of a commercial dental high carat gold alloy, 65·5wt% Au–14·0wt% Ag–10·0wt% Cu–8·9wt% Pt, was investigated by means of hardness testing, X‐ray diffraction study and scanning electron microscopy. Age‐hardening was generated by the coherency strain resulting from the transformation of the α single phase to the Ag‐rich α1 phase and the AuCu I type ordered phase. The coherency strain seemed to be associated with the nucleation of the AuCu ordered structure initially, and then was brought about with the simultaneous formation of the Ag‐rich α1 phase and the AuCu I type ordered phase. Hardening was attributed mainly to the very fine coherent precipitates of a lamellar structure composed of the Ag‐rich α1 phase and the AuCu I type ordered phase at grain boundaries, and softening, which occurred following prolonged ageing, was due to the coarsening of the fine lamellar structure by releasing the strain at the interfaces of the adjacent lamellae.