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Description
Grain boundary is a type of 2-dimensional (2D) defect that appears in the interface between two grains in a polycrystal. It has a different structure compared to the grain interior, directly affecting the properties of the bulk material, such as strength, ductility, fracture, and corrosion. In nanocrystalline systems, grain boundaries become a dominant factor due to the increase in grain boundary density when compared to systems on the microscopic scale. Grain boundary engineering (GBE) has been showing significant progress in manipulating grain boundaries during the past decades. However, these methods are usually restricted to a limited number of systems, such as segregation and second phase precipitation, or by relying upon numerous steps that end up causing dimensional and microstructural changes in the grain's interior. This research proposes a new grain boundary engineering strategy to fulfill the need for a more localized method using a hybrid thermal elastic processing (TEP). This method consists of applying uniaxial stress, either tension or compression, and storing elastic energy inside the sample without plastic deformation. Next, the sample is put under short annealing, still under uniaxial stress. Then the material is cooled down to room temperature, and the stresses are removed. The central hypothesis is that the thermally activated inhomogeneous release of elastic stress-energy between grain boundary and grain interior can generate faceting of the interface. Faceted grain boundaries represent a reduction in the grain boundary energy, which was proven beneficial for bulk properties such as resistance to intergranular fracture and corrosion. Molecular dynamic simulation was used to apply the TEP to pure aluminum bicrystals with symmetric tilt grain boundary and different misorientations. The results showed positive results, where all grain boundary morphologies presented changes from liner to faceted boundaries under specific setups. The TEP settings were also analyzed experimentally, achieving preliminary results on the potential of TEP method and allowing for improvement of experimental setups for future works.
