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A Low-gold Dental Alloy: Structure and Segregations
H. Herø
NIOM, Scandinavian Institute of Dental Materials, Oslo, Norway
R. Jørgensen
NIOM, Scandinavian Institute of Dental Materials, Oslo, Norway
E. Sørbrøden
Department of Physics, University of Oslo, Oslo, Norway
The structure and concentration gradients were studied in the as-cast state for a low-gold alloy and a conventional Type III gold alloy. A much more lamellar eutectic phase was found at the grain boundaries in the low-gold alloy. TEM investigations showed that the interior of the grains consisted of fine lamellae, which probably were alternating Au-Ag and Au-Cu-rich bands due to the miscibility gap in the solid state. Microprobe analyses, where the beam overlapped several of the observed lamellae, displayed both the inter-dendritic and grain boundary segregations to be much larger for the low-gold alloy than for the Type III alloy. The lamellae observed in the as-cast state are quickly dissolved at 700°C into one phase, but the relaxation by diffusion of the concentration differences associated with grain boundary segregations required several hours because of the much larger distances involved. Aging at 350°C caused precipitation of ordered fct particles. On the basis of structure and alloy composition, they are most likely AuCu I and may contain some Pd.
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Journal of Dental Research, Vol. 61, No. 11,
1292-1298 (1982)
DOI: 10.1177/00220345820610111601
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