Electron backscatter diffraction studies of focused ion beam induced phase transformation in cobalt

Abstract

A focused ion beam microscope was used to induce cubic to hexagonal phase transformation in a cobalt alloy, of similar composition to that of the binder phase in a hardmetal, in a controlled manner at 0°, 45° and 80° ion incident angles. The cobalt had an average grain size of ~20μm, allowing multiple orientations to be studied, exposed to a range of doses between 6×107 and 2×1010 ions/μm2. Electron backscatter diffraction (EBSD) was used to determine the original and induced phase orientations, and area fractions, before and after the ion beam exposure. On average, less phase transformation was observed at higher incident angles and after lower ion doses. However there was an orientation effect where grains with an orientation close to {111} planes were most susceptible to phase transformation, and {101} the least, where grains partially and fully transformed at varying ion doses.