Temperature influence on the faceting of SIGMA 3 and OMEGA 9 grain boundaries in Cu

摘要

The faceting of a tube-like tilt grain boundary (GB) in Cu bicrystals has been studied in the temperature interval from 05 to 0,95 of the melting temperature T_m (T_m = 1356 K). The grains of the bicrystals form the coincidence site lattice (CSL) with inverse density of coincidence sites SIGMA = 3 and SIGMA = 9, No rounded edges between facets were observed up to 0.95T_m. With decreasing temperature new facets of increasingly higher CSL indices appear. At 0.5T_m six crystallographically different SIGMA = 3 facets exist simultaneously,. The appearance of high-index CSL facets can be explained by the roughening phase transition of a Kosterlitz-Thouless type. The ratio of GB energy sigma_(GB) and surface energy sigma_(sur) of the specimen was measured by applying atomic force microscopy to the profile of the GB thermal groove formed upon additional annealing. The Wulff-Herring diagrams were constructed using measured sigma_(GB)/sigma_(sur) values.