High-resolution electron microscopy and electron diffraction were applied to elucidate the hardening mechanism in an 18-carat gold commercial dental alloy, Au-31.7 at.%,Cu-8.1 at.%,Pd-5.3 at.%,Ag-54.9 at.%. The interface between the AuCu-I ordered platelets and the surrounding Au3Cu ordered phase was anilyzed down to the atomic scale. A geometric model for the interface was deduced directly from the high-resolution electron micrographs. No evidence was found for the presence of a FCC phase at the interface between AuCu-I and Au 3Cu.
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