Grain growth and twin formation in a Ag-4Pd alloy ribbon after annealing treatments

Abstract

In this study, the microstructural evolution of Ag-4Pd ribbon under various annealing conditions was investigated via electron backscatter diffraction (EBSD) technique. The as-manufactured Ag-4Pd ribbon, with an initial grain size of 3.66 µm and twin density of 53.1%, was held under different annealing treatment conditions of 623–1073 K for time periods of 0.5–100 h. The grain size distribution showed that after prolonged annealing treatment, the distribution deviated from the normal distribution, indicating that abnormal grain growth occurred. The grain growth time exponent (n) was calculated to be 0.35 and decreased with annealing temperature. The activation energy obtained from the growth rate of the grains was found to be 1.46 eV, indicating the dominance of grain boundary diffusion. The deviation of the n value and activation energy from those of pure silver could be attributed to the alloying Pd content and the presence of abundant twin boundaries within the microstructure of the Ag-4Pd ribbon, which was confirmed by EBSD results. The mechanical behavior of this material is also discussed, providing insight into a theoretical basis for application in a high-power IC module.