[Age--hardening in Au-8wt%Pd alloys containing small quantities of indium (part 1) (author's transl)].

Age-hardening was produced by the additions of minor amounts of indium to a Au-Pd-base alloy for metal-ceramics, as in the Au-Pt-based ternary alloys. (1) The age-hardening, detected from the electrical resistance measurement and hardness test, increased with increasing indium contents in the Au-Pd-In ternary alloys, but was not responsible in a Au-Pd-base alloy. (2) Photomicrographs of the ternary alloys demonstrated the characteristic microstructures in the age-hardened state, but did not appear the intragranular precipitations in the as-casted and the solution-annealed state. A nodular reaction at the grain boundary was shown in the initial aging stage, subsequently the precipitations in the matrix resulted with increasing in hardness. The typical Widmannstätten's structure was developed with the over-aged stage. (3) The matrix phase in the Au-Pd-base ternary alloys containing indium was indexed by X-ray diffraction to a face-centered cubic structure. The lattice parameters were found within a=4.05 A to a=4.06 A, and then increased with indium contents. (4) The cause of the age-hardening has been implied during to the formation of intermetallic compounds, i.e. Pd-In system, but the structures can not been identified in the age-hardening state.