Direct observation of intergranular stress fields in polycrystalline materials

The ability to measure interparticle stress fields is crucial for a number of scientific fields, Detailed knowledge of such interaction stresses can shed light on a number of phenomena such as the fracture mechanics of polycrystalline materials, the mechanics of granular media, and crystallization process of microspheres and nanospheres. In this letter we report the use of a new micro-Raman-spectroscopy-based technique to measure directly the intergranular stress fields in polycrystalline systems. Using Raman active tracers (50 Angstrom graphite crystals) dispersed in the system, the technique was shown to be applicable for non-Raman-active polycrystalline systems (e.g. metals). For the first time, stresses within and around individual grains has been monitored in situ as the global system stress was increased to system failure. The effects of grain orientation and shape are monitored and discussed.