Transmission electron microscopic investigation of a Pd–Ag–In–Sn dental alloy

With the price volatility of palladium, there has been renewed interest in palladium–silver alloys for metal-ceramic restorations in dentistry. The microstructures of a popular Pd–Ag dental alloy were investigated in the as-cast and simulated porcelain-firing heat-treated conditions, using transmission electron microscopy. In the as-cast condition, the microstructure was strongly influenced by microsegregation, and contained the face-centered cubic Pd solid solution matrix, a eutectic structure with lattice parameters that varied for the two phases, and a face-centered tetragonal (fct) precipitate. After heat treatment, the lattice parameters for the two phases in the eutectic structure were uniform, and discontinuous precipitates with {0 1 1}matrix habit planes and dislocations appeared in the matrix. An unusual nanostructured constituent was found in the fct set of eutectic lamellae in the heat-treated alloys.