Nanoindentation identifications of mechanical properties of Cu6Sn5, Cu3Sn, and Ni3Sn4 intermetallic compounds derived by diffusion couples

We report in this paper Young's moduli and hardness of Cu6Sn5, Cu3Sn, and Ni3Sn4 intermetallic compounds (IMCs) measured by nanoindentation. The samples were prepared by annealing Sn-Cu and Sn-Ni diffusion couples. Indentations performed along the directions lateral and perpendicular to the IMC layers show statistically indistinguishable Young's moduli and hardness for each of the three IMCs, implying that these polycrystalline IMC aggregates are rather isotropic. Nanomechanical responses of the IMCs were shown to depend greatly on the strain rate during loading while independent of the strain rate during unloading. Multiple pop-in events were observed for Cu6Sn5 during loading at a strain rate lower than about 0.1-0.5 s-1. Topographies of the residual impressions were quantitatively measured and the pile-up features were apparent for the three IMCs.