Influence of Crystal Structure on Helium-induced Nano-tendril Formation in a Multiphase, Multicomponent Alloy

Plasma-facing materials (PFMs) for magnetic fusion will experience a unique set of challenges, including plasma-surface interactions. In tungsten, helium ions diffuse through the surface resulting in the formation of nano-tendrils which may contaminate the fusion plasma. Multicomponent alloys are being considered as alternative PFMs though little is known about how they will behave in a plasma environment. Using a focused helium beam provided by a helium ion microscope (HIM), we irradiated equiatomic FeCoCrNiV, which comprises FCC and BCT crystal structures with similar compositions, enabling us to determine the influence of crystal structure on the formation of nano-tendrils. Irradiations were performed up to 500°C, and fluences between 6x1017 and 1x1020 He ions/cm2. Here, we present HIM images from the irradiated regions, and cross-sectional TEM/EDX images on selected samples. The data reveals a critical temperature for tendril formation dependant on crystal structure, helium bubbles, and helium-induced changes in composition.