Age-hardening characteristics of a dental low-carat gold alloy with dual hardener system of In and CuReport as inadecuate

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Gold Bulletin

, Volume 44, Issue 4, pp 223–230

First Online: 29 October 2011


The age-hardening characteristics of a dental low carat gold alloy with a dual hardener system of indium In and Cu 33.9 Au–26.2 Ag–20.28 Cu–9.8 Pd–7.8 In–2 Zn at% were examined by observing the age hardenability and related phase transformation, microstructural changes and elemental distribution during the aging process at 400°C. The dual hardener system by the use of both In and Cu provided more powerful hardening effect compared to a single-hardener system of In or Cu, without the formation of a AuCu type ordered phase. The alloy showed apparent initial hardening, which was attributed to the pre-precipitation or zone formation by the help of quenched in excess vacancies. During the constant increase in hardness, the single parent phase separated into three phases, Au–Ag-based phase, Au–Cu-based phase containing Pd and In, and InPd-based phase, through a metastable state. Indium which was added as one of the hardeners induced initial grain boundary precipitation, followed by an expansion of the lamellar structure, which was responsible for softening. The alternative lamellar structure was composed of a Cu-rich layer Au–Cu-based phase containing Pd and In and an Ag-rich layer Au–Ag-based phase replaced partly by the InPd-based phase. Separation of the Ag-rich layer from the Cu-rich layer is based on the miscibility limit of Ag and Cu due to their eutectic property.

KeywordsDual hardener system Age-hardening characteristics Phase transformation Au–Ag–Cu–Pd–In Alternative lamellar structure  Download fulltext PDF

Author: Hyo-Joung Seol - Seong-Woo Kweon - Su-Yeon Cho - Gwang-Young Lee - Yong Hoon Kwon - Hyung-Il Kim


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