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KMID : 0362220120390040261
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Journal of The Korean Research Society for Dental Materials
2012 Volume.39 No. 4 p.261 ~ p.268
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Phase Transformation and Microstructural Changes of a Dental Au-Ag-Cu-Pd Alloy Containing Small Amounts of Zn and In
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Kim Bu-Sob
Park Mi-Gyoung
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Abstract
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Age-hardening behaviour of a low-carat gold alloy composed of 47.87 wt % Au-37.12 wt % Ag-8.64 wt % Cu-5.62 wt % Pd-0.49 wt % Zn-0.26 wt % In was investigated, and the following results were obtained. 1. At an early stage of the aging process, the hardness increased rapidly. Then, hardness continued to increase rapidly until the maximum value, and appeared to decrease apparently with aging time. 2. By aging the solution-treated specimen, the parent fcc phase was transformed into the solute-depleted Ag-Au-based phase, AuCu I phase containing Pd and Zn, and InPd phase containing Cu and Zn. 3. The hardness increased due to the formation of lattice strain at the interface between the matrix fcc phase and product fcc and fct AuCu I phases during the nucleation of the AuCu I phase from the matrix phase. The hardness decreased due to the loss of lattice strains by the formation and coarsening of lamellar structure composed of the AuCu I and solute-depleted Ag-Au-based phases. 4. The precipitation of a minor, InPd phase containing Cu and Zn, occurred in the later stage of the aging process and did not have an effect on the increase of hardness.
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KEYWORD
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Au-Ag-Cu-Pd, Age-hardening behaviour, InPd phase, Phase transformation
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