Journal of Dental Research, Vol 61, 1292-1298, Copyright © 1982 by International & American Associations for Dental Research Online Journals
A low-gold dental alloy: structure and segregations
H. Hero, R. Jorgensen and E. Sorbroden
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 interdendritic 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 degrees 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 degrees C cause precipitation of
ordered fct particles. On the basis of structure and alloy composition,
they are most likely AuCu I and may contain some Pd.
