[Effects of Au content on ageing characteristics of Dental AG-Pd-Cu-Au alloys (I). Ageing characteristics of the alloys quenched from 800 degrees C designated by JIS as solution treatment temperature (author's transl)].

Commercial Ag-Pd-Cu-Au alloys of which Au content was changed form 0 to 50 wt. % were quenched from 800 degrees designated by JIS as solution treatment temperature and aged isochronically. The maximum hardness of the alloys by ageing decreased with increasing the Au content. Shape of age-hardening curve of the alloys was divided into two groups, one was of the lower Au content alloys containing below 30 wt. / Au and the other was of the higher Au content alloys containing more than 40 wt. % Au. As quenched structure of the lower Au content alloys was mixture of f.c.c alpha 2 phase and L20 type ordered phase (beta phase), on the other hand, the higher Au content alloys was composed simply by f.c.c alpha phase only. The maximum hardness of the lower Au content alloys given by ageing was caused by precipitates appeared at grain boundary, and of the higher Au content alloys was caused by precipitates in the grain were found. These facts may suggest that the mechanism of age hardening for the alloys change with increasing the Au content.