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Abstract

Mechanical properties of individual interfaces have a strong influence on the deformation behaviour of metallic microstructures. For mesoscale models of deformation and fracture we need on the one hand characteristic material properties such as the work of separation, the energy barriers for interface sliding, or the tensile or shear strength of the interfaces. On the other hand the underlying mechanisms are of interest, such as shearing via rigid sliding, migration, or dislocation emission, or brittle and ductile fracture. Ideally, structure, properties, and mechanisms should be related by a physics based model. In this presentation I'll introduce some of our contributions to the long-standing effort to link grain boundary structure to properties, and properties to mechanisms, via atomistic simulations of interfaces under shear and tensile load.

We could show that there are relationships between characteristic quantities, such as stacking fault energies, and the mechanisms of shearing at the interfaces of lamellar TiAl by molecular dynamics simulations. The comparison with similar boundaries in pure Al also demonstrates the influence of the crystal structure.

Ab-initio tensile tests of grain boundaries in different crystal structures, with different geometry, and chemistry confirmed that mechanical models based on fundamental properties exist, which remain valid under a variation of all the abovementioned variables. However, the explicit expression which relates them to the geometric degrees of freedom is still missing. The details of the missing links and potential steps to establish them will be discussed in the presentation.