Dynamical interaction of helium bubbles with grain boundaries in Fe and Fe–9Cr ferritic alloy

Dynamical interaction of helium bubbles with grain boundaries in Fe and Fe–9Cr has been studied by in situ electron microscopy and thermal desorption spectroscopy (TDS). It is clearly demonstrated that most small helium bubbles are swept to the specimen surface by dynamical interaction with the moving grain boundaries during re-crystallization, which induces easy motion along the boundary. At small angle grain boundaries, helium bubbles are frequently trapped at grain boundary dislocations and move along the dislocation line. The bubble diffusivity along the grain boundary dislocation is statistically estimated from the moving path and the value is similar to or a little higher than that in the matrix. Well correlated and enhanced thermal desorption spectra with the sweeping of helium bubbles by moving grain boundaries in Fe and Fe–9Cr are revealed.