Investigation of the Influence of Nanoscale Porosity in the Interfacial Layers on the Mechanical Properties of Helium Plasma-Exposed Tungsten

Abstract

Porous layers emergent from the bulk tungsten (W) interface subsequent to helium (He) plasma exposure, under conditions relevant to thermonuclear experiments, were found to significantly modulate the structural attributes of the W─as deduced through nanoscale indentation measurements. Plastic deformation of nanofibers constituting the fuzzy surface layer, along with an increased yield strength with layer depth, was quantified. A power-law relationship between the indentation modulus (Eind) and the porosity of the fuzzy W was indicated. The surface roughness of the bulk W increases with temperature prior to fuzz formation, determined by AFM. A decrease in the Eind of the bulk W underneath the fuzzy layer with increasing sample temperature when exposed to plasma, in agreement with molecular-dynamics computations, was observed.