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Abstract

Modern structural materials are seldom single crystals, but exhibit a polycrystalline, multiphase, often hierarchical microstructure. Nowadays tailored microstructures are within experimental reach that contain favourable arrangements of grain boundaries. The specific properties of these interfaces can even be tuned by segregation engineering. This gives additional impetus to the developement of predictive material models that bridge between the atomistic details of grain boundaries and the effective properties of the microstructure, and can help to identify microstructures with optimised mechanical properties.
Numerical simulation methods that either allow the study of relevant processes on their individual characteristic length scale, or that can be used to pass on information from finer to coarser length scales, are common tools in this respect. In the area of modelling deformation and fracture of metallic microstructures, so-called cohesive zone models are a promising option to include interface-specific behaviour in a mesoscale simulation. In these models the cohesive properties like cleavage energies, shear and tensile strength, are part of the traction-separation laws, which determine the response of the respective interface to a mechanical load. These properties, and even the complete traction-separation laws, can be obtained from atomistic simulations.
In the presentation examples of atomistic studies of grain boundaries in TiAl and Al will be given that illustrate current achievements, but also the challenges that one has to face when trying to extract effective mechanical behaviour and to link it to fundamental physical and geometrical properties of the interfaces, not only for use in multiscale modelling, but also to deepen our undestanding of interface mechanics.