Utilizing In Situ TEM to Decipher the Nanomechanical Properties of Helium Implanted Metals

In nuclear energy systems, materials exposed to helium will form bubbles and cavities within the microstructure due to helium accumulation and segregation to defects and interfaces. Combined with high temperatures and irradiation conditions, these bubbles can lead to degradation of mechanical properties such as embrittlement, cracking, and surface nanostructure development, all of which can affect material safety and bulk performance. These impacts can be observed in bulk scale mechanical tests, although macroscale mechanical testing can wash-out the microscale mechanisms dictating the material response. However, small-scale mechanical testing in the scanning or transmission electron microscopes can elucidate in real time the processes the drive the mechanical behavior. In this work, we investigate the influence of helium implantation on the mechanical property performance of erbium and erbium hydride, which exhibits bubble formation and surface blistering following helium accumulation. Utilizing in-situ transmission electron microscopy and scanning electron microscopy mechanical testing on erbium, erbium-hydride, and helium-implanted erbium hydride, we investigate the mechanical performance under nano/micro-scale straining conditions including compression and bending. With real time imaging and stress-strain measurements, the microstructural features are correlated with deformation behavior to quantify the effects of helium loading to be able to identify nanoscale helium bubbles with the micro-to-nano scale mechanical performance. Analysis of the load-displacement data will correlate displacement events leading to mechanical failure with microstructural changes. Coupled with meso-scale finite element modelling, we compare the impact of the hydriding and helium implantation on the mechanical behavior to allow for an accurate prediction of material property evolution during exposure to and accumulation of helium during material use.<br/>Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.