Hardness and Composition of Solution-Treated Ag-Pd-Cu-Au Alloy Microstructures

Abstract

An Ag-Pd-Cu-Au casting alloy was subjected to solution treatment at various temperatures. The dynamic hardness of each resultant microstructure and the Vickers hardness of the whole alloy were measured to investigate their relationship with changes in metal and crystal structure of the alloy and microstructural elemental concentration. The samples following solution treatment at 650, 700, 750, and 800 C consisted of a fine-layer structure (Structure A), a rough-layer structure (Structure B), and an island-like structure (Structure C). Structures A and B, after treatment at 850 C, were indistinguishable. The composition of Structure A was very similar to that of the alloy. Structures B and C were Ag-rich/Pd-poor/Cu-poor and Ag-poor/Pd-rich/Cu-rich, respectively. The composition of Structures B and C approached that of Structure A with increasing treatment temperature. The dynamic hardness, which was highest in Structure A, lower in Structure C, and lowest in Structure B, increased with increasing treatment temperature. These findings suggest that solid solution strengthening, due to elemental diffusion between structures during heating, contributes to hardening at elevated solution treatment temperatures.

Combinatorial Study of Gradient Ag–Al Thin Films: Microstructure, Phase Formation, Mechanical and Electrical Properties

“…As can be seen, the hardness was increased by alloying Ag with Al. In the fcc-Ag region, 6–13 atom % Al, the hardness is slightly higher than the pure Ag reference value, which is due to the effect of solid solution strengthening. , However, in this region, a slight decrease at 10–13 atom % can be observed. This can be attributed to the porous structure as seen in Figure b.…”