Grain boundary ridges slow dawn grain boundary motion: In-situ observation

• The behavior of the GB system with different ridges in Zn was studied in situ.
• For the first time the values of GB ridge mobility were measured for “facet-to-rough” and “rough-to-rough” ridges.
• The first order ridge impacts the kinetics of GB motion.
• Faceted GBs with two “facet-to-rough” ridges move one order of magnitude slower in comparison with curved GB with one “rough–rough” ridge.

The impact of grain boundary (GB) ridge on motion of high-angle GB in Zn was studied. The steady-state motion of faceted GB half-loop with [101¯0] tilt GB and GB ridge was recorded in-situ. The temperatures of faceting–roughening transition were experimentally defined for three GB half-loops. Above the transition temperature GB half-loops had GB “rough-to-rough” ridge with continuously curved GB segments. Below the transition temperature a facet appeared and coexisted with two “facet-to-rough” ridges. For the first time we could extract mobility of “rough-to-rough” and “rough-to-facet” ridges and bring out clearly that GB ridge slows down GB motion. Present removes contradiction between high facet mobility and the low mobility of faceted GB.