Measurement of the grain boundary energy of commercially-pure grade 2 titanium at high temperature

The formation of grains and their growth based on the elimination of other grains, before thermal cycles are imposed, are essential for the correct conformation of a material and to control the microstructure, texture and orientation relationships between phases. However, when the boundary of a polycrystalline grain intersects the outer surface and the material is exposed to temperatures higher than half of its fusion temperature, a crack or groove appears. This research aims to apply a method to evaluate the energy of the grain boundary (GB) and also to compare the energy values of the faces of the GB, and to investigate commercially-pure grade 2 titanium in relation to the action of forces on the grain boundary of the free surface. The thermal attack under vacuum technique was used to reveal, at high temperatures, the titanium microstructure, which is preserved under a very thin oxide layer even when the sample is brought to room temperature. Thus, at room temperature, it was possible to analyze the Ti surface viewed at high temperature. The thermal cracks or grooves appearing due to the selective vaporization of atoms at the GB were measured geometrically using atomic force microscopy. The energy relationship of the GB was determined from the microstructural appearance at high temperatures and applying the equation g gb = 2·g s ·senj to the thermal crack formed between two grains.The results were compared experimentally with others reported in the literature. With the method applied in this study it was possible to evaluate the energy of the GB and it was verified that this energy was anisotropic for the material