Place: DPG Spring Meeting 2009, Dresden, Germany
To investigate the role of grain boundaries during deformation and fracture of polycrystalline materials, we perform an ab-initio density functional study of a series of special grain boundaries in aluminium. The goal is to find relationships between the characteristic mechanical properties of interfaces - such as the work of separation, and the grain boundary sliding resistance - and the grain boundary degrees of freedom. We perform ”ab-initio tensile tests”at bulk and bicrystal supercells to determine the effective interface elastic constant, the work of separation, as well as the critical stress and displacement for cleavage. The results will be discussed with respect to the grain boundary character (tilt/twist) and misorientation angle. Information on grain boundary sliding can be gained by studying the -surface of the interface, E(), with being a rigid shift parallel to the grain boundary. The morphology of the surface depends on the periodicity of the interface, and thus again on the grain boundary degrees of freedom, and the nature of the chemical bonds. Several -surfaces will be compared and the different influences discussed.