Age Hardening and Conductivity in CuPd-Ag Ternary Alloys

Age hardening kinetics and ordered phase stability across the Pd-Cu-Ag ternary system were investigated. Compositions ranged from 40-50 at.% Pd and 50-60 at.% Cu—within the vicinity of the CuPd phase field—with ternary silver additions up to 8 at.%. Using in-situ four-wire resistance measurements during thermal processing, we compared the hardening response between cold-worked (HTCW) and annealed (HTA) conditions across 35 distinct compositions. Two primary experimental protocols were employed: isothermal aging at 400°C of annealed material, and stepped temperature profiles for HTCW samples to identify both ordering completion and subsequent disordering behavior. Results revealed composition-dependent aging rates with silver additions directly correlating with the age hardening rate. Ag additions enabled higher rate of age hardening than could be accomplished via optimization of the Cu:Pd ratio alone. These findings established processing-structure-property relationships essential in the development of a new Pd-Cu-Ag spring alloy for semiconductor test applications, Paliney® 35.