Second-order faceting–roughening of the tilt grain boundary in zinc

Abstract

Abstract The faceting of the almost stationary tilt grain boundary with a misorientation angle of 84° in the Zn bicrystal has been investigated. The shape of the very slow migrating grain boundary has been studied in situ between 350 and 400 °C using polarized light. Two intersecting facets lie in the closely-packed planes of the constrained coincidence sites lattice with coincidence parameter = 15. In the as-grown sample flat grain boundary facets form the sharp first-order ridge with the break of the first derivative y/x of the grain boundary shape similar to those observed in our previous works on GB faceting in Zn. However, above 350 °C the sharp first-order ridge is substituted by the smooth grain boundary portion without a ∂y/∂x derivative break similar to that observed in twin grain boundaries in Mo. The transformation of the as-grown first-order grain boundary ridge into continuous one has been observed for the first time. The critical parameter α has been calculated using the grain boundary shape in the transition region. α increases from α = 1.7 ± 0.07 for 350 °C to α = 1.9 ± 0.07 for 385 °C approaching the α = 2 value predicted in the mean-field Andreev model for the continuous surface roughening.