Two representative Pd-Cu-Ga dental alloys, one with a dendritic as-cast microstructure containing a eutectic interdendritic constituent and the other with an equiaxed fine-grained as-cast microstructure containing a near-surface eutectic constituent, have been subjected to rapid quenching following casting, in addition to the conventional bench cooling recommended by the manufacturers. The quenched alloys were subsequently heat treated at temperatures of 1200°, 1500° and 1800 op that span the range of the firing cycles for dental porcelain. Scanning electron microscopic examination showed that the lamellar eutectic constituents normally present in the microstructures of the as-cast and bench-cooled alloys persisted when the alloys were rapidly quenched after casting, although microstructural changes were evident. A large decrease occurred in the Vickers hardness of the alloy with the dendritic as-cast microstructure after heat treatment at 1500°F, and in the hardness of both alloys after heat treatment at 1800°F.
Brantley, William A.; Cai, Zhuo; Vermilyea, Stanley G.; Papazoglou, Efstratios; Mitchell, John C.; and Carr, Alan B.
"Effects of Solidification Conditions and Heat Treatment on the Microstructure and Vickers Hardness of Pd-Cu-Ga Dental Alloys,"
Cells and Materials: Vol. 6
, Article 14.
Available at: http://digitalcommons.usu.edu/cellsandmaterials/vol6/iss1/14