Abstract
Abstract The important role of grain boundaries for the mechanical properties of polycrystalline materials has been recognized for many decades. Up to now, the underlying deformation mechanisms at the nano- and micro scale are not understood quantitatively. An overview of the synthesis and subsequent mechanical testing of specific grain boundaries at the micro and sub-micro scale is discussed in the present contribution, including various methods for producing one or multiple specific, crystallographically well-defined grain boundaries. Furthermore, established micromachining methods for isolating and measuring local dislocation-grain boundary interactions are portrayed. Examples of the techniques described are shown with to the aid of copper grain boundaries.
Highlights
The important role of grain boundaries for the mechanical properties of polycrystalline materials has been recognized since many decades
One reason here is that the collective deformation of a large number of differently oriented grains, with numerous, largely different grain boundaries (GBs) blurs the individual interaction modes observed at one GB
Within this chapter we focus on the isolation of individual dislocation-GB interactions by producing micron and submicron sized samples well-suited for mechanical testing
Summary
To unravel the dislocation-GB interaction modes for one specific GB two general approaches for material synthesis can be applied: Fabrication of bi-crystals possessing a specific GB and Fabrication of polycrystalline materials possessing multiple a priori undefined GBs. A “two-dimensional” microstructure with columnar grains and vertical GBs is formed upon very long annealing times (up to three days at 0.85 of melting temperature of a material [20]) Another prerequisite for getting extended, straight GB segments is a mirror surface finish and an absence of oxide layers before annealing. If successfully applied, this method allows testing differently oriented, hundreds of microns long vertical GBs. the GBs structure and chemistry can hardly be controlled requiring an extensive search for the desired GB by e.g. EBSD-SEM
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