Microscale deformation behavior of bicrystal boundaries in pure tin (Sn) using micropillar compression

Uniaxial compression experiments on micron-sized bicrystalline and single-crystalline pillars in tin (Sn) using a flat punch nanoindenter tip, have enabled us to quantify the difference in stress-strain behavior associated with grain boundaries in tin. It was found that bicrystalline micropillars containing a twin boundary nearly parallel to the loading axis were characterized by numerous strain bursts and a yield stress either lower than or comparable to its single-crystalline counterparts. Transmission electron microscopy on the deformed micropillar revealed that the twin boundary migration is associated with partial dislocation activity. The slip systems interacting with the boundary have also been identified using stereographic projections. Micropillar compression indicated different findings for bicrystalline pillars containing random angle grain boundaries, which displayed strengthening by acting as a barrier to dislocation glide. These results indicate that the grain boundary character plays a very crucial role in controlling the mechanical response of Sn-rich solder joints and provide insights into the deformations mechanisms occurring at different boundaries.