Anahita Khorashadizadeh

Star-Shaped Crystallographic Cracking of Localized Nanoporous Defects

On self-assembled monolayer-covered Cu-Au substrates, localized volume shrinkage at initial dealloying sites leads to cracks within the attacked regions. It is started from well-controlled surface structures to gain fundamental insights in the driving mechanisms of localized corrosion and crack formation. Both the crack density and the crack morphology are critically dependent on surface orientation, crystallography, and inhibitor molecule species.

3D Tomographic EBSD Measurements of Heavily Deformed Ultra Fine Grained Cu-0.17wt%Zr Obtained from ECAP

Obtaining knowledge on the grain boundary topology in three dimensions is of great importance as it controls the mechanical properties of polycrystalline materials. In this study, the three dimensional texture and grain topology of as-deformed ultra fine grained Cu-0.17wt%Zr have been investigated using three-dimensional orientation microscopy (3D electron backscattering diffraction, EBSD) measurements in ultra fine grained Cu-0.17wt%Zr. Equal channel angular pressing was used to produce the ultra fine grained structure. The experiments were conducted using a dual-beam system for 3D-EBSD. The approach is realized by a combination of a focused ion beam (FIB) unit for serial sectioning with high-resolution field emission scanning electron microscopy equipped with EBSD. The work demonstrates that the new 3D EBSD-FIB technique provides a new level of microstructure information that cannot be achieved by conventional 2D-EBSD analysis.

Self‐Assembled Monolayers: Star‐Shaped Crystallographic Cracking of Localized Nanoporous Defects (Adv. Mater. 33/2015)

On page 4877, F. U. Renner, A. Bashir, M. Valtiner, and co-workers describe a star-like dealloying corrosion morphology that appears during the localized attack of smooth well-prepared Cu-Au surfaces. The surfaces are initially protected by thiol or selenol inhibitior films. Localized dealloying of Cu-Au produces nanoporous gold under stress and crystallographic cracks - thereby opening a new approach combining surface science with nanoscale mechanical testing.

Analysis of 3D-EBSD Datasets Obtained by FIB Tomography

3D-EBSD represents a destructive and crystallographic tomographic method. It comprises a repeated sectioning and subsequent surface characterization by Electron Backscatter Diffraction (EBSD). Several sectioning alternatives exist, most widespread though, is an integrated in-situ sectioning technique in which an SEM based focused ion beam (FIB) is applied to generate accurately spaced serial sections.

Recrystallization and Grain Growth in Ultra Fine Grained Materials Produced by High Pressure Torsion

Investigations of the microstructure of materials processed via severe plastic deformation methods such as high pressure torsion (HPT) and their recrystallization behaviour is of great interest as they are capable of producing ultra fine grained material (UFD) with good mechanical properties.