Retardation of Grain Boundary Reactions in Ag–Cu Alloys by Addition of Tin
The grain boundary reactions in Ag-Cu alloys with or without 1.5 mass%Sn were investigated by optical microscope, electric resistivity, SEM, and hardness tests. The results are summarized as follows. Electric resistivity, hardness, and nodule formation were investigated as a function of aging time for 93Ag-7Cu and 91.6Ag-6.9Cu-1.5Sn alloys at temperatures between 250 and 350 o C. With aging time, the electric resistivity of Sn-added alloy decreased rapidly and reached a constant value after passing a minimum. In the 91.6Ag-6.9Cu-1.5Sn alloy, very fine particles of β-Cu were precipitated in the α'-Ag phase with Cu supersaturation at the initial stage of the aging treatment at each temperature, while nodule formation was significantly retarded