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KMID : 1035320190460040229
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Korean Society for Dental Materials
2019 Volume.46 No. 4 p.229 ~ p.242
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Changes in hardness and microstructure of a Pd-Ag-In-Ga-based metal-ceramic alloy during porcelain firing simulation and subsequent cooling
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Shin Hye-Jung
Kwon Yong-Hoon
Seol Hyo-Joung
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Abstract
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In this experiment, the alloy having the composition of 49.5Pd-40Ag-9In-1Ga (wt.%) was used to find the most effectivecooling rate for the hardening of alloy during porcelain firing simulation. In each stage of firing simulation, ice-quenchingor cooling at the most effective cooling rate for hardening of the alloy was done after firing to observe changes in the hardnessand associated microstructures during the firing and subsequent cooling. For this purpose, the firing simulated alloy was characterizedby analyzing the changes in hardness, microstructure, crystal structure and the elemental distribution. The hardness of alloydecreased by cooling after oxidation treatment, which was induced by the homogenization of the specimen. In this alloy, themost effective cooling rate for alloy hardening after oxidation treatment was Stage 0. During the porcelain firing simulationuntil the final firing stage, the cooling rate was set to Stage 0, and the complete firing simulation was performed until thefinal firing stage, Glaze. As a result, the final hardness of the metal substructure obtained after complete firing simulation waslower than that of the as-cast specimen. The decrease in hardness caused by the porcelain firing simulation results from areduction in the interface between the precipitates of face-centered tetragonal structures and the matrix of face-centered cubicstructures as the precipitates coarsen.
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KEYWORD
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Cooling rate, Homogenization, Porcelain firing simulation, Precipitation
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