Motion of the faceted 57 ½1120 tilt grain boundary in zinc

The impact of faceting on the high-angle grain boundary motion was studied. The non-steady-state motion of the 57 ½1120 tilt grain boundary (GB) half-loop in a Zn bicrystal has been studied in situ. Above 678 K the slowly migrating GB half-loop was continuously curved. Below this temperature moving GB was fully or partially faceted. The transformation of curved GB into a GB facet with increasing temperature was observed for the first time. Overlapping faceting/roughening of three crystallograpically different GB facets lead to the complicated nonsteady- state motion. As a result, the GB mobility values and migration enthalpy were not unique, but lay in a certain interval.