Helium Implantation of Ultrafine Grained Tungsten within a TEM

Abstract

ABSTRACTMany theoretical predictions have suggested that the confined length scales and increased interface density of various nanostructured materials may result in desired thermal, mechanical, and radiation properties. An important aspect of this for next generation nuclear reactors is understanding the change in swelling resulting from helium evolution in tungsten alloys, as a function of grain size and grain boundary type. This study investigated this using a new ion irradiation transmission electron microscope (TEM) facility that has been developed at Sandia National Laboratories and is capable of ion implanting helium at energies up to 20 keV. It was demonstrated in this feasibility study that helium could be implanted into an ultrafine grained tungsten TEM sample produced by severe plastic deformation. The size and density of the helium bubbles formed during the experiment appear nearly constant; while the larger voids formed appear to be dependent on the local microstructure. Future work is underway to both optimize the facility, as well as better understand the evolution of ultrafine grained tungsten resulting from both helium implantation and displacement damage.