[Studies on the aging characteristics of gold alloys used for metal-ceramics restorations--age-hardening mechanism in a Au-8 wt%Pd-4 wt%In alloy. (Part 2) (author's transl)].

Abstract

The age-hardening mechanism in a Au-8wt%Pd ternary alloy containing 4wt+In were investigated by means of electrical resistivity measurement, hardness test, transmission electron microscopy, X-ray microanalysis and diffractions. The following conclusions had been drawn. 1. Two maxima in resistivity appeared during isochronal aging. These changes were also observed during isothermal aging. Each depended on the aging temperature and time, respectively. 2. The first maximum in resistivity was considered to be due to the formation of the short range order clustering promoted by the addition of indium to the gold-palladium binary alloy. 3. The second maximum in resistivity was due to the spinodal decomposition. 4. The rapid decreasing in resistivity during the isochronal or isothermal aging was due to the formation of modulated structures attended by the separation of ordered phases. 5. These precipitates determined by X-ray microdiffraction method were two intermetallic compounds ordered ortho type Pd2In and fct type Pd3In. 6. It was concluded that the mechanism of age-hardening in this alloy was due to the formation of modulated structures being accompanied by the precipitation of Pd2In and Pd3In from the supersaturated solid solution.