Precipitation Hardening in a Dental Low-gold Alloy.

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

“…Therefore, it is believed that the extremely fine nature of the lamellar structure supplied large amounts of inter-phase boundaries, which contain lattice strain by difference in lattice parameter between the solutedepleted Au-rich layer and the precipitated layer of the lamellar structure. Therefore, the subsequent microstructural coarsening that reduces the inter-phase boundaries results in softening, as has also been observed in various dental agehardenable alloys [18][19][20][21]. Considering the immediate lamellar formation, the restorations made by the Pt-added-Au-based metal-ceramic alloys can be strengthened easily during the firing process for porcelain by the introduction of a fine lamellar structure.…”

“…On the other hand, in the present study, the Pd content was slightly higher in the Pt-concentrated region (b-P) than in the Pt-depleted region (b-M). This appears to be because Pd normally tends to form a stable phase with elements having a relatively low melting temperature, such as In and Sn [21]. In the G.I region for the specimen aged at 550°C for 20,000 min, the elemental distribution was similar to that of the single-phased matrix of the solution-treated specimen (a-M) due to the fine nature of the grain interior precipitates and solute-depleted matrix in the grain interior.…”