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KMID : 1035320150420040327
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Korean Society for Dental Materials
2015 Volume.42 No. 4 p.327 ~ p.334
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Effects of repeated casting on hardness of a Pd-Ag-Au metal-ceramic alloy
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Cho Mi-Hyang
Lee Gwang-Young
Cho Su-Yoen
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Abstract
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Dental alloy manufacturers advise against the reuse of previously melted alloy. However, for economic and environmental reasons, dental laboratories often reuse the casting surplus. The purpose of present study is to find out the reason in hardness change of a Pd-Ag-Au-In-Sn metal-ceramic alloy by recasting. Hardness decreased with increase in casting frequency. At the same time, the microstructure of all recasted specimen showed complex microstructural features. The recasted specimens were composed of the matrix and the particle-like structures covered with fine precipitates. The decrease in hardness by recasting was caused by the decrease of nuclei concentration by repeated melting and resultant increase in grain size. The precipitates covered with the particle-like structures showed no microstructural change by the repeated casting up to 5 times. It was indicated that the precipitates were not related to the change in hardness by recasting.
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KEYWORD
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Pd-Ag-Au-In-Sn alloy, recasting, grain growth, hardness
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